Bug 1525760 - Add a clang-based base toolchains task. r=froydnj

These are copies of the corresponding gcc-based base toolchain tasks,
with FORCE_GCC and the gcc dependency removed.

We also tweak things a little for those builds to actually end up green.

Differential Revision: https://phabricator.services.mozilla.com/D18903

--HG--
extra : moz-landing-system : lando

browser/app/no-pie/moz.build

@@ -17,6 +17,12 @@ CFLAGS += [
 
 # Use OS_LIBS instead of LDFLAGS to "force" the flag to come after -pie
 # from MOZ_PROGRAM_LDFLAGS.
-OS_LIBS += [
+if CONFIG['CC_TYPE'] == 'clang':
+    # clang < 5.0 doesn't support -no-pie.
+    OS_LIBS += [
+        '-nopie'
+    ]
+else:
+    OS_LIBS += [
         '-no-pie'
-]
+    ]

build/unix/mozconfig.unix

@@ -13,8 +13,15 @@ else
     CC="$TOOLTOOL_DIR/clang/bin/clang"
     CXX="$TOOLTOOL_DIR/clang/bin/clang++"
     export ENABLE_CLANG_PLUGIN=1
+    case "$PERFHERDER_EXTRA_OPTIONS" in
+    base-toolchains*)
+      # Clang versions < 7.0 don't support the -fcrash-diagnostics-dir flag.
+      ;;
+    *)
       export CFLAGS="$CFLAGS -fcrash-diagnostics-dir=${UPLOAD_PATH}"
       export CXXFLAGS="$CXXFLAGS -fcrash-diagnostics-dir=${UPLOAD_PATH}"
+      ;;
+    esac
 
     if [ -n "$MOZ_PGO" ]; then
         if [ -z "$USE_ARTIFACT" ]; then

taskcluster/ci/build/linux.yml

@@ -313,6 +313,70 @@ linux64-base-toolchains/debug:
         - linux64-sccache
         - linux64-node
 
+linux64-base-toolchains-clang/opt:
+    description: "Linux64 base toolchains clang Opt"
+    index:
+        product: firefox
+        job-name: linux64-base-toolchains-clang-opt
+    treeherder:
+        platform: linux64/opt
+        symbol: Bbc
+    worker-type: aws-provisioner-v1/gecko-{level}-b-linux
+    worker:
+        docker-image: {in-tree: debian7-amd64-build-base}
+        max-run-time: 7200
+        env:
+            PERFHERDER_EXTRA_OPTIONS: base-toolchains-clang
+    run:
+        using: mozharness
+        actions: [get-secrets, build, check-test]
+        config:
+            - builds/releng_base_firefox.py
+            - builds/releng_base_linux_64_builds.py
+        script: "mozharness/scripts/fx_desktop_build.py"
+        secrets: true
+        tooltool-downloads: public
+        need-xvfb: true
+    toolchains:
+        - linux64-clang-3.9
+        - linux64-rust-1.31
+        - linux64-cbindgen
+        - linux64-sccache
+        - linux64-node
+
+linux64-base-toolchains-clang/debug:
+    description: "Linux64 base toolchains clang Debug"
+    index:
+        product: firefox
+        job-name: linux64-base-toolchains-clang-debug
+    treeherder:
+        platform: linux64/debug
+        symbol: Bbc
+    worker-type: aws-provisioner-v1/gecko-{level}-b-linux
+    worker:
+        docker-image: {in-tree: debian7-amd64-build-base}
+        max-run-time: 3600
+        env:
+            PERFHERDER_EXTRA_OPTIONS: base-toolchains-clang
+    run:
+        using: mozharness
+        actions: [get-secrets, build, check-test]
+        config:
+            - builds/releng_base_firefox.py
+            - builds/releng_base_linux_64_builds.py
+        script: "mozharness/scripts/fx_desktop_build.py"
+        secrets: true
+        custom-build-variant-cfg: debug
+        mozconfig-variant: debug
+        tooltool-downloads: public
+        need-xvfb: true
+    toolchains:
+        - linux64-clang-3.9
+        - linux64-rust-1.31
+        - linux64-cbindgen
+        - linux64-sccache
+        - linux64-node
+
 linux/opt:
     description: "Linux32 Opt"
     index: