Bug 1726114 - Use clang toolchain for macosx native builds. r=firefox-build-system-reviewers,mhentges

For plain builds, that puts them more in line with local builds.

Differential Revision: https://phabricator.services.mozilla.com/D122824

taskcluster/ci/build/macosx-native.yml

@@ -36,6 +36,7 @@ macosx64-plain/opt:
     run-on-projects: ['mozilla-central']
     fetches:
         toolchain:
+            - macosx64-clang
             - macosx64-cbindgen
             - macosx64-nasm
             - macosx64-node
@@ -67,6 +68,7 @@ macosx64-plain/debug:
     run-on-projects: ['trunk']
     fetches:
         toolchain:
+            - macosx64-clang
             - macosx64-cbindgen
             - macosx64-nasm
             - macosx64-node
@@ -97,6 +99,7 @@ macosx64-rusttests/opt:
     run-on-projects: ['mozilla-central']
     fetches:
         toolchain:
+            - macosx64-clang
             - macosx64-rust
             - macosx64-cbindgen
             - macosx64-nasm
@@ -127,6 +130,7 @@ macosx64-rusttests/debug:
     run-on-projects: ['trunk']
     fetches:
         toolchain:
+            - macosx64-clang
             - macosx64-rust
             - macosx64-cbindgen
             - macosx64-nasm