Bug 1616694 - Turn the macosx-cross toolchain task into a mere repackage r=nalexander

Currently the macosx-cross toolchain build pulls in a linux64-clang toolchain, uses it to build a Mac native toolchain, and then clobbers the result with pieces of the Linux toolchain. This means that the same version of LLVM is used to build the Mac pieces and be part of the final artifact. This will become a problem with upcoming LLVM 11 where we'll want to build the Mac pieces with LLVM 9 but otherwise repackage an LLVM 11 Linux toolchain.

So this commit makes the macosx-cross workflow look more like the win-cross one: take two compilers built elsewhere and just merge them.

Differential Revision: https://phabricator.services.mozilla.com/D83378

taskcluster/ci/toolchain/clang.yml

@@ -172,27 +172,20 @@ linux64-clang-9-macosx-cross:
         symbol: TL(clang9-macosx-cross)
     worker-type: b-linux
     worker:
-        max-run-time: 3600
-        env:
-            TOOLTOOL_MANIFEST: "browser/config/tooltool-manifests/macosx64/cross-releng.manifest"
+        max-run-time: 600
     run:
         script: build-clang-linux-macosx-cross.sh
-        arguments:
-            - 'build/build-clang/clang-macosx64.json'
-        resources:
-            - 'build/build-clang/clang-macosx64.json'
-            - 'taskcluster/scripts/misc/tooltool-download.sh'
         toolchain-alias: linux64-clang-macosx-cross
         toolchain-artifact: public/build/clang.tar.zst
-        tooltool-downloads: internal
+    dependencies:
+        macosx64-clang-9: toolchain-macosx64-clang-9
     fetches:
-        fetch:
-            - clang-9
         toolchain:
-            - linux64-binutils
-            - linux64-cctools-port-clang-9
             - linux64-clang-9
-            - linux64-gcc-7
+        macosx64-clang-9:
+            # Put this into a new directory so it doesn't conflict with the linux toolchain
+            - artifact: clang.tar.zst
+              dest: clang-mac
 
 linux64-clang-9-win-cross:
     description: "Clang 9 toolchain build with Windows Compiler RT libs"

taskcluster/scripts/misc/build-clang-linux-macosx-cross.sh

@@ -4,34 +4,15 @@ set -x -e -v
 # This script is for building clang for Mac OS X targets on a Linux host,
 # including native Mac OS X Compiler-RT libraries and llvm-symbolizer.
 
-cd $GECKO_PATH
-
-. taskcluster/scripts/misc/tooltool-download.sh
-
-# these variables are used in build-clang.py
-export CROSS_CCTOOLS_PATH=$MOZ_FETCHES_DIR/cctools
-export CROSS_SYSROOT=$(ls -d $MOZ_FETCHES_DIR/MacOSX10.*.sdk)
-export PATH=$PATH:$CROSS_CCTOOLS_PATH/bin
-
-# gets a bit too verbose here
-set +x
-
-cd $MOZ_FETCHES_DIR/llvm-project
-python3 $GECKO_PATH/build/build-clang/build-clang.py -c $GECKO_PATH/$1 --skip-tar
-
-# We now have a native macosx64 toolchain.
-# What we want is a native linux64 toolchain which can target macosx64 and use the sanitizer dylibs.
-# Overlay the linux64 toolchain that we used for this build (except llvm-symbolizer).
-(
-cd build/stage1
-# Need the macosx64 native llvm-symbolizer since this gets shipped with sanitizer builds
-mv clang/bin/llvm-symbolizer $MOZ_FETCHES_DIR/clang/bin/
-cp --remove-destination -lr $MOZ_FETCHES_DIR/clang/* clang/
-tar -c clang | $GECKO_PATH/taskcluster/scripts/misc/zstdpy > $MOZ_FETCHES_DIR/llvm-project/clang.tar.zst
-)
-
-set -x
-
-# Put a tarball in the artifacts dir
 mkdir -p $UPLOAD_DIR
-cp clang.tar.* $UPLOAD_DIR
+cd $MOZ_FETCHES_DIR
+
+# We have a native linux64 toolchain in $MOZ_FETCHES_DIR/clang
+# We have a native macosx64 toolchain in $MOZ_FETCHES_DIR/clang-mac/clang
+# What we want is a mostly-linux64 toolchain but with a macosx64 llvm-symbolizer and runtime libraries
+
+mv clang-mac/clang/bin/llvm-symbolizer clang/bin/
+cp --remove-destination -lr clang/* clang-mac/clang/
+
+cd clang-mac
+tar -c clang | $GECKO_PATH/taskcluster/scripts/misc/zstdpy > $UPLOAD_DIR/clang.tar.zst