Bug 1758781 - Use the WinMsvc.cmake toolchain file to build compiler-rt. r=firefox-build-system-reviewers,mhentges

The toolchain file is a helper for cross-compilation that even deals
with case-sensivity in MSVC, which simplifies our setup.

Differential Revision: https://phabricator.services.mozilla.com/D140710

taskcluster/ci/toolchain/compiler-rt.yml

@@ -183,7 +183,6 @@ win32-compiler-rt-13:
             - clang-13
         toolchain:
             - linux64-clang-13-stage1
-            - linux64-liblowercase
 
 win64-compiler-rt-13:
     description: "win64 x64 Compiler-rt for Clang 13 toolchain build"
@@ -205,7 +204,6 @@ win64-compiler-rt-13:
             - clang-13
         toolchain:
             - linux64-clang-13-stage1
-            - linux64-liblowercase
 
 wasm32-wasi-compiler-rt-13:
     description: "wasm32-wasi Compiler-rt for Clang 13 toolchain build"

taskcluster/scripts/misc/build-compiler-rt.sh

@@ -109,35 +109,13 @@ case "$target" in
   "
   ;;
 *-pc-windows-msvc)
-  VSPATH="$MOZ_FETCHES_DIR/vs2017_15.9.6"
-  SDK_VERSION=10.0.17134.0
-
-  export INCLUDE="${VSPATH}/VC/include;${VSPATH}/VC/atlmfc/include;${VSPATH}/SDK/Include/${SDK_VERSION}/ucrt;${VSPATH}/SDK/Include/${SDK_VERSION}/shared;${VSPATH}/SDK/Include/${SDK_VERSION}/um"
-  case "$target" in
-  i686-pc-windows-msvc)
-    VCARCH=x86
-    ;;
-  x86_64-pc-windows-msvc)
-    VCARCH=x64
-    ;;
-  aarch64-pc-windows-msvc)
-    VCARCH=arm64
-    ;;
-  esac
-  export LIB="${VSPATH}/VC/lib/${VCARCH};${VSPATH}/VC/atlmfc/lib/${VCARCH};${VSPATH}/SDK/Lib/${SDK_VERSION}/um/${VCARCH};${VSPATH}/SDK/Lib/${SDK_VERSION}/ucrt/${VCARCH}"
-  export LD_PRELOAD=$MOZ_FETCHES_DIR/liblowercase/liblowercase.so
-  export LOWERCASE_DIRS=$VSPATH
-  clang=$MOZ_FETCHES_DIR/clang/bin/clang-cl
-  clangxx=$clang
-  ar=lib
   EXTRA_CMAKE_FLAGS="
-    -DCMAKE_SYSTEM_NAME=Windows
-    -DCMAKE_LINKER=$MOZ_FETCHES_DIR/clang/bin/lld-link
-    -DCMAKE_MT=$MOZ_FETCHES_DIR/clang/bin/llvm-mt
-    -DCMAKE_RC_COMPILER=$MOZ_FETCHES_DIR/clang/bin/llvm-rc
-    -DCMAKE_C_FLAGS='--target=$target -fms-compatibility-version=19.15.26726'
-    -DCMAKE_CXX_FLAGS='--target=$target -fms-compatibility-version=19.15.26726'
-    -DCMAKE_ASM_FLAGS=--target=$target
+    -DCMAKE_TOOLCHAIN_FILE=$MOZ_FETCHES_DIR/llvm-project/llvm/cmake/platforms/WinMsvc.cmake
+    -DLLVM_NATIVE_TOOLCHAIN=$MOZ_FETCHES_DIR/clang
+    -DMSVC_BASE=$MOZ_FETCHES_DIR/vs2017_15.9.6/VC
+    -DWINSDK_BASE=$MOZ_FETCHES_DIR/vs2017_15.9.6/SDK
+    -DWINSDK_VER=10.0.17134.0
+    -DHOST_ARCH=${target%-pc-windows-msvc}
   "
   ;;
 *)
@@ -146,6 +124,20 @@ case "$target" in
   ;;
 esac
 
+case "$target" in
+*-pc-windows-msvc)
+  ;;
+*)
+  EXTRA_CMAKE_FLAGS="
+    $EXTRA_CMAKE_FLAGS
+    -DCMAKE_C_COMPILER=$clang
+    -DCMAKE_CXX_COMPILER=$clang++
+    -DCMAKE_AR=$MOZ_FETCHES_DIR/clang/bin/llvm-ar
+    -DCMAKE_RANLIB=$MOZ_FETCHES_DIR/clang/bin/llvm-ranlib
+  "
+  ;;
+esac
+
 if [ -n "$TOOLTOOL_MANIFEST" ]; then
   . $GECKO_PATH/taskcluster/scripts/misc/tooltool-download.sh
 fi
@@ -169,13 +161,9 @@ done
 eval cmake \
   $MOZ_FETCHES_DIR/llvm-project/compiler-rt \
   -GNinja \
-  -DCMAKE_C_COMPILER=$clang \
-  -DCMAKE_CXX_COMPILER=${clangxx:-$clang++} \
   -DCMAKE_C_COMPILER_TARGET=$target \
   -DCMAKE_CXX_COMPILER_TARGET=$target \
   -DCMAKE_ASM_COMPILER_TARGET=$target \
-  -DCMAKE_AR=$MOZ_FETCHES_DIR/clang/bin/llvm-${ar:-ar} \
-  -DCMAKE_RANLIB=$MOZ_FETCHES_DIR/clang/bin/llvm-ranlib \
   -DCMAKE_BUILD_TYPE=Release \
   -DCMAKE_INSTALL_PREFIX=${PWD}/${dir} \
   -DLLVM_ENABLE_ASSERTIONS=OFF \