diff --git a/taskcluster/ci/toolchain/clang.yml b/taskcluster/ci/toolchain/clang.yml
index 91baa8d83335..81182c542e89 100644
--- a/taskcluster/ci/toolchain/clang.yml
+++ b/taskcluster/ci/toolchain/clang.yml
@@ -387,6 +387,101 @@ win64-clang-14-stage1:
         toolchain:
             - win64-vs2019
 
+linux64-clang-trunk-mingw-x86:
+    description: "MinGW-Clang trunk x86 toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TMW(clang-trunk-x86)
+    worker-type: b-linux
+    run:
+        script: build-clang-mingw.sh
+        arguments:
+            - 'x86'
+        toolchain-artifact: public/build/clangmingw.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+            - mingw-w64
+            - llvm-mingw
+            - gcc-9.4.0
+        toolchain:
+            - linux64-clang-trunk
+
+linux64-clang-trunk-mingw-x64:
+    description: "MinGW-Clang trunk x64 toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TMW(clang-trunk-x64)
+        tier: 1
+    worker-type: b-linux
+    run:
+        script: build-clang-mingw.sh
+        arguments:
+            - 'x64'
+        toolchain-artifact: public/build/clangmingw.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+            - mingw-w64
+            - llvm-mingw
+            - gcc-9.4.0
+        toolchain:
+            - linux64-clang-trunk
+
+linux64-clang-trunk-stage1:
+    description: "Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TL(clang-trunk-stage1)
+    run:
+        using: toolchain-script
+        script: build-clang.sh
+        arguments:
+            - 'build/build-clang/linux64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/1stage.json'
+        resources:
+            - 'build/build-clang/linux64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/1stage.json'
+        toolchain-artifact: public/build/clang.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-toolchain-sysroot
+
+linux64-clang-trunk-profile:
+    description: "Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TL(clang-trunk-profile)
+    run:
+        using: toolchain-script
+        script: build-clang.sh
+        arguments:
+            - 'build/build-clang/linux64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/skip-stage-1.json'
+            - 'build/build-clang/profile.json'
+        resources:
+            - 'build/build-clang/linux64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/skip-stage-1.json'
+            - 'build/build-clang/profile.json'
+        toolchain-artifact: public/build/merged.profdata
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - linux64-x64-compiler-rt-trunk
+            - linux64-toolchain-sysroot
+
 linux64-clang-trunk-raw:
     description: "Clang trunk toolchain build"
     attributes:
@@ -394,22 +489,24 @@ linux64-clang-trunk-raw:
     treeherder:
         symbol: TL(clang-trunk-raw)
     run:
-        using: toolchain-script
         script: build-clang.sh
         arguments:
             - 'build/build-clang/linux64.json'
             - 'build/build-clang/clang-trunk.json'
-            - 'build/build-clang/2stages.json'
+            - 'build/build-clang/skip-3-stages.json'
+            - 'build/build-clang/4stages-pgo.json'
         resources:
             - 'build/build-clang/linux64.json'
             - 'build/build-clang/clang-trunk.json'
-            - 'build/build-clang/2stages.json'
+            - 'build/build-clang/skip-3-stages.json'
+            - 'build/build-clang/4stages-pgo.json'
         toolchain-artifact: public/build/clang.tar.zst
-    run-on-projects: []
     fetches:
         fetch:
             - clang-trunk
         toolchain:
+            - linux64-clang-trunk-stage1
+            - linux64-clang-trunk-profile
             - linux64-toolchain-sysroot
 
 linux64-clang-trunk:
@@ -424,8 +521,221 @@ linux64-clang-trunk:
     run:
         script: repack-clang.sh
         toolchain-artifact: public/build/clang.tar.zst
-    run-on-projects: []
     fetches:
         toolchain:
+            - linux64-cctools-port
             - linux64-clang-trunk-raw
-            - wasm32-wasi-compiler-rt
+            - android-aarch64-compiler-rt-trunk
+            - android-arm-compiler-rt-trunk
+            - android-x64-compiler-rt-trunk
+            - android-x86-compiler-rt-trunk
+            - linux64-aarch64-compiler-rt-trunk
+            - linux64-x64-compiler-rt-trunk
+            - linux64-x86-compiler-rt-trunk
+            - macosx64-aarch64-compiler-rt-trunk
+            - macosx64-x64-compiler-rt-trunk
+            - wasm32-wasi-compiler-rt-trunk
+            - win32-compiler-rt-trunk
+            - win64-compiler-rt-trunk
+
+macosx64-clang-trunk-raw:
+    description: "Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TM(clang-trunk-raw)
+    worker-type: b-linux-large
+    worker:
+        max-run-time: 3600
+    run:
+        script: build-clang.sh
+        arguments:
+            - 'build/build-clang/macosx64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/skip-3-stages.json'
+            - 'build/build-clang/4stages-pgo.json'
+        resources:
+            - 'build/build-clang/macosx64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/skip-3-stages.json'
+            - 'build/build-clang/4stages-pgo.json'
+        toolchain-artifact: public/build/clang.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-cctools-port
+            - linux64-clang-trunk-stage1
+            - linux64-clang-trunk-profile
+            - macosx64-sdk-11.0
+            - macosx64-x64-compiler-rt-trunk
+
+macosx64-clang-trunk:
+    description: "Clang trunk toolchain repack with MacOS Compiler RT libs"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TM(clang-trunk)
+    worker-type: b-linux
+    worker:
+        max-run-time: 600
+    run:
+        script: repack-clang.sh
+        toolchain-artifact: public/build/clang.tar.zst
+    fetches:
+        toolchain:
+            - linux64-cctools-port
+            - macosx64-clang-trunk-raw
+            - android-aarch64-compiler-rt-trunk
+            - android-arm-compiler-rt-trunk
+            - android-x64-compiler-rt-trunk
+            - android-x86-compiler-rt-trunk
+            - linux64-aarch64-compiler-rt-trunk
+            - linux64-x64-compiler-rt-trunk
+            - linux64-x86-compiler-rt-trunk
+            - macosx64-aarch64-compiler-rt-trunk
+            - macosx64-x64-compiler-rt-trunk
+            - wasm32-wasi-compiler-rt-trunk
+            - win32-compiler-rt-trunk
+            - win64-compiler-rt-trunk
+
+macosx64-aarch64-clang-trunk-raw:
+    description: "Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TM(clang-trunk-aarch64-raw)
+    worker-type: b-linux-large
+    worker:
+        env:
+            OSX_ARCH: arm64
+        max-run-time: 3600
+    run:
+        script: build-clang.sh
+        arguments:
+            - 'build/build-clang/macosx64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/skip-3-stages.json'
+            - 'build/build-clang/4stages-pgo.json'
+        resources:
+            - 'build/build-clang/macosx64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/skip-3-stages.json'
+            - 'build/build-clang/4stages-pgo.json'
+        toolchain-artifact: public/build/clang.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-cctools-port
+            - linux64-clang-trunk-stage1
+            - linux64-clang-trunk-profile
+            - macosx64-sdk-11.0
+            - macosx64-aarch64-compiler-rt-trunk
+
+macosx64-aarch64-clang-trunk:
+    description: "Clang trunk toolchain repack with MacOS Compiler RT libs"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TM(clang-trunk-aarch64)
+    worker-type: b-linux
+    worker:
+        max-run-time: 600
+    run:
+        script: repack-clang.sh
+        toolchain-artifact: public/build/clang.tar.zst
+    fetches:
+        toolchain:
+            - linux64-cctools-port
+            - macosx64-aarch64-clang-trunk-raw
+            - macosx64-aarch64-compiler-rt-trunk
+            - macosx64-x64-compiler-rt-trunk
+            - wasm32-wasi-compiler-rt-trunk
+
+win64-clang-trunk-raw:
+    description: "Clang-cl trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TW64(clang-trunk-raw)
+    worker-type: b-win2012
+    worker:
+        max-run-time: 9000
+    run:
+        script: build-clang.sh
+        arguments:
+            - 'build/build-clang/win64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/skip-stage-1-win64.json'
+            - 'build/build-clang/4stages-pgo.json'
+        resources:
+            - 'build/build-clang/win64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/skip-stage-1-win64.json'
+            - 'build/build-clang/4stages-pgo.json'
+        toolchain-artifact: public/build/clang.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+            - cmake
+            - ninja
+        toolchain:
+            - win64-clang-trunk-stage1
+            - win64-compiler-rt-trunk
+            - win64-vs2019
+
+win64-clang-trunk:
+    description: "Clang-cl trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TW64(clang-trunk)
+    worker-type: b-linux
+    worker:
+        max-run-time: 600
+    run:
+        script: repack-clang.sh
+        toolchain-artifact: public/build/clang.tar.zst
+    fetches:
+        toolchain:
+            - linux64-cctools-port
+            - win64-clang-trunk-raw
+            - android-aarch64-compiler-rt-trunk
+            - android-arm-compiler-rt-trunk
+            - android-x64-compiler-rt-trunk
+            - android-x86-compiler-rt-trunk
+            - linux64-aarch64-compiler-rt-trunk
+            - linux64-x64-compiler-rt-trunk
+            - linux64-x86-compiler-rt-trunk
+            - macosx64-aarch64-compiler-rt-trunk
+            - macosx64-x64-compiler-rt-trunk
+            - wasm32-wasi-compiler-rt-trunk
+            - win32-compiler-rt-trunk
+            - win64-compiler-rt-trunk
+
+win64-clang-trunk-stage1:
+    description: "Clang-cl trunk toolchain build stage 1"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TW64(clang-trunk-stage1)
+    worker-type: b-win2012
+    run:
+        script: build-clang.sh
+        arguments:
+            - 'build/build-clang/win64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/1stage.json'
+        resources:
+            - 'build/build-clang/win64.json'
+            - 'build/build-clang/clang-trunk.json'
+            - 'build/build-clang/1stage.json'
+        toolchain-artifact: public/build/clang.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+            - cmake
+            - ninja
+        toolchain:
+            - win64-vs2019
diff --git a/taskcluster/ci/toolchain/compiler-rt.yml b/taskcluster/ci/toolchain/compiler-rt.yml
index 9af19bf62360..85a9088e4b0b 100644
--- a/taskcluster/ci/toolchain/compiler-rt.yml
+++ b/taskcluster/ci/toolchain/compiler-rt.yml
@@ -225,3 +225,242 @@ wasm32-wasi-compiler-rt-14:
             - wasi-sdk
         toolchain:
             - linux64-clang-14-stage1
+
+android-aarch64-compiler-rt-trunk:
+    description: "android aarch64 Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TA(aarch64-crt-trunk)
+    run:
+        arguments:
+            - build/build-clang/clang-trunk.json
+        resources:
+            - build/build-clang/clang-trunk.json
+            - taskcluster/scripts/misc/build-llvm-common.sh
+        toolchain-artifact: public/build/compiler-rt-aarch64-linux-android.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - linux64-android-ndk-linux-repack
+
+android-arm-compiler-rt-trunk:
+    description: "android arm Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TA(arm-crt-trunk)
+    run:
+        arguments:
+            - build/build-clang/clang-trunk.json
+        resources:
+            - build/build-clang/clang-trunk.json
+            - taskcluster/scripts/misc/build-llvm-common.sh
+        toolchain-artifact: public/build/compiler-rt-armv7-linux-android.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - linux64-android-ndk-linux-repack
+
+android-x86-compiler-rt-trunk:
+    description: "android x86 Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TA(x86-crt-trunk)
+    run:
+        arguments:
+            - build/build-clang/clang-trunk.json
+        resources:
+            - build/build-clang/clang-trunk.json
+            - taskcluster/scripts/misc/build-llvm-common.sh
+        toolchain-artifact: public/build/compiler-rt-i686-linux-android.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - linux64-android-ndk-linux-repack
+
+android-x64-compiler-rt-trunk:
+    description: "android x64 Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TA(x64-crt-trunk)
+    run:
+        arguments:
+            - build/build-clang/clang-trunk.json
+        resources:
+            - build/build-clang/clang-trunk.json
+            - taskcluster/scripts/misc/build-llvm-common.sh
+        toolchain-artifact: public/build/compiler-rt-x86_64-linux-android.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - linux64-android-ndk-linux-repack
+
+linux64-x86-compiler-rt-trunk:
+    description: "Linux x86 Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TL(x86-crt-trunk)
+    run:
+        arguments:
+            - build/build-clang/clang-trunk.json
+        resources:
+            - build/build-clang/clang-trunk.json
+            - taskcluster/scripts/misc/build-llvm-common.sh
+        toolchain-artifact: public/build/compiler-rt-i686-unknown-linux-gnu.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - sysroot-i686-linux-gnu
+
+linux64-x64-compiler-rt-trunk:
+    description: "Linux x64 Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TL(x64-crt-trunk)
+    run:
+        arguments:
+            - build/build-clang/clang-trunk.json
+        resources:
+            - build/build-clang/clang-trunk.json
+            - taskcluster/scripts/misc/build-llvm-common.sh
+        toolchain-artifact: public/build/compiler-rt-x86_64-unknown-linux-gnu.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - sysroot-x86_64-linux-gnu
+
+linux64-aarch64-compiler-rt-trunk:
+    description: "Linux aarch64 Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TL(aarch64-crt-trunk)
+    run:
+        arguments:
+            - build/build-clang/clang-trunk.json
+        resources:
+            - build/build-clang/clang-trunk.json
+            - taskcluster/scripts/misc/build-llvm-common.sh
+        toolchain-artifact: public/build/compiler-rt-aarch64-unknown-linux-gnu.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - sysroot-aarch64-linux-gnu
+
+macosx64-x64-compiler-rt-trunk:
+    description: "macOS x64 Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TM(x64-crt-trunk)
+    run:
+        arguments:
+            - build/build-clang/clang-trunk.json
+        resources:
+            - build/build-clang/clang-trunk.json
+            - taskcluster/scripts/misc/build-llvm-common.sh
+        toolchain-artifact: public/build/compiler-rt-x86_64-apple-darwin.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - macosx64-sdk-11.0
+
+macosx64-aarch64-compiler-rt-trunk:
+    description: "macOS aarch64 Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TM(aarch64-crt-trunk)
+    run:
+        arguments:
+            - build/build-clang/clang-trunk.json
+        resources:
+            - build/build-clang/clang-trunk.json
+            - taskcluster/scripts/misc/build-llvm-common.sh
+        toolchain-artifact: public/build/compiler-rt-aarch64-apple-darwin.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - macosx64-sdk-11.0
+
+win32-compiler-rt-trunk:
+    description: "win32 x86 Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TW32(crt-trunk)
+    run:
+        arguments:
+            - build/build-clang/clang-trunk.json
+        resources:
+            - build/build-clang/clang-trunk.json
+            - taskcluster/scripts/misc/build-llvm-common.sh
+        toolchain-artifact: public/build/compiler-rt-i686-pc-windows-msvc.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - linux64-liblowercase
+            - win64-vs2019
+
+win64-compiler-rt-trunk:
+    description: "win64 x64 Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TW64(crt-trunk)
+    run:
+        arguments:
+            - build/build-clang/clang-trunk.json
+        resources:
+            - build/build-clang/clang-trunk.json
+            - taskcluster/scripts/misc/build-llvm-common.sh
+        toolchain-artifact: public/build/compiler-rt-x86_64-pc-windows-msvc.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+        toolchain:
+            - linux64-clang-trunk-stage1
+            - linux64-liblowercase
+            - win64-vs2019
+
+wasm32-wasi-compiler-rt-trunk:
+    description: "wasm32-wasi Compiler-rt for Clang trunk toolchain build"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TL(wasi-crt-trunk)
+    worker-type: b-linux-xlarge
+    run:
+        script: build-compiler-rt-wasi.sh
+        toolchain-artifact: public/build/compiler-rt-wasm32-wasi.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+            - wasi-sdk
+        toolchain:
+            - linux64-clang-trunk-stage1
diff --git a/taskcluster/ci/toolchain/sysroot.yml b/taskcluster/ci/toolchain/sysroot.yml
index b494d6782e44..4e506313f71b 100644
--- a/taskcluster/ci/toolchain/sysroot.yml
+++ b/taskcluster/ci/toolchain/sysroot.yml
@@ -63,15 +63,16 @@ sysroot-x86_64-linux-gnu-x11:
         arguments:
             - amd64
 
-sysroot-wasm32-wasi:
+sysroot-wasm32-wasi-clang-14:
     description: "Sysroot for wasi"
     attributes:
         local-toolchain: true
     run-on-projects: [trunk]
     treeherder:
-        symbol: TL(sysroot-wasi)
+        symbol: TL(sysroot-wasi-14)
     run:
         script: build-sysroot-wasi.sh
+        toolchain-alias: sysroot-wasm32-wasi
         toolchain-artifact: public/build/sysroot-wasm32-wasi.tar.zst
     fetches:
         fetch:
@@ -80,6 +81,22 @@ sysroot-wasm32-wasi:
         toolchain:
             - linux64-clang-14
 
+sysroot-wasm32-wasi-clang-trunk:
+    description: "Sysroot for wasi"
+    attributes:
+        cached_task: false
+    treeherder:
+        symbol: TL(sysroot-wasi-trunk)
+    run:
+        script: build-sysroot-wasi.sh
+        toolchain-artifact: public/build/sysroot-wasm32-wasi.tar.zst
+    fetches:
+        fetch:
+            - clang-trunk
+            - wasi-sdk
+        toolchain:
+            - linux64-clang-trunk
+
 sysroot-aarch64-linux-gnu:
     description: "Sysroot for linux64 aarch64 builds"
     attributes:
diff --git a/taskcluster/scripts/misc/build-compiler-rt.sh b/taskcluster/scripts/misc/build-compiler-rt.sh
index 698c96ad3d64..89e7c6d44be1 100755
--- a/taskcluster/scripts/misc/build-compiler-rt.sh
+++ b/taskcluster/scripts/misc/build-compiler-rt.sh
@@ -13,6 +13,13 @@ case "$target" in
     -DCOMPILER_RT_BUILD_ORC=OFF
   "
   ;;
+*-apple-darwin)
+  EXTRA_CMAKE_FLAGS="
+    -DCOMPILER_RT_ENABLE_IOS=OFF
+    -DCOMPILER_RT_ENABLE_WATCHOS=OFF
+    -DCOMPILER_RT_ENABLE_TVOS=OFF
+  "
+  ;;
 esac
 
 EXTRA_CMAKE_FLAGS="
diff --git a/taskcluster/scripts/misc/build-llvm-common.sh b/taskcluster/scripts/misc/build-llvm-common.sh
index 7e3c8d7c9186..d7890c5d21f1 100755
--- a/taskcluster/scripts/misc/build-llvm-common.sh
+++ b/taskcluster/scripts/misc/build-llvm-common.sh
@@ -122,18 +122,29 @@ case "$target" in
 *-pc-windows-msvc)
   export LD_PRELOAD="/builds/worker/fetches/liblowercase/liblowercase.so"
   export LOWERCASE_DIRS="/builds/worker/fetches/vs"
-  # WinMsvc.cmake before LLVM 15 doesn't support spaces in WINDSK_BASE. LLVM 15+ uses
-  # different input variables.
-  ln -s "windows kits/10" $MOZ_FETCHES_DIR/vs/sdk
   EXTRA_CMAKE_FLAGS="
     $EXTRA_CMAKE_FLAGS
     -DCMAKE_TOOLCHAIN_FILE=$MOZ_FETCHES_DIR/llvm-project/llvm/cmake/platforms/WinMsvc.cmake
     -DLLVM_NATIVE_TOOLCHAIN=$MOZ_FETCHES_DIR/clang
-    -DMSVC_BASE=$MOZ_FETCHES_DIR/vs/vc/tools/msvc/14.29.30133
-    -DWINSDK_BASE=$MOZ_FETCHES_DIR/vs/sdk
-    -DWINSDK_VER=10.0.19041.0
     -DHOST_ARCH=${target%-pc-windows-msvc}
+    -DLLVM_DISABLE_ASSEMBLY_FILES=ON
   "
+  # LLVM 15+ uses different input variables.
+  if grep -q LLVM_WINSYSROOT $MOZ_FETCHES_DIR/llvm-project/llvm/cmake/platforms/WinMsvc.cmake; then
+    EXTRA_CMAKE_FLAGS="
+      $EXTRA_CMAKE_FLAGS
+      -DLLVM_WINSYSROOT=$MOZ_FETCHES_DIR/vs
+    "
+  else
+    # WinMsvc.cmake before LLVM 15 doesn't support spaces in WINDSK_BASE.
+    ln -s "windows kits/10" $MOZ_FETCHES_DIR/vs/sdk
+    EXTRA_CMAKE_FLAGS="
+      $EXTRA_CMAKE_FLAGS
+      -DMSVC_BASE=$MOZ_FETCHES_DIR/vs/vc/tools/msvc/14.29.30133
+      -DWINSDK_BASE=$MOZ_FETCHES_DIR/vs/sdk
+      -DWINSDK_VER=10.0.19041.0
+    "
+  fi
   ;;
 *)
   echo $target is not supported yet