Bug 1685599 - Build aarch64-compiler-rt using clang-11 instead of clang-11-macosx-cross. r=firefox-build-system-reviewers,mhentges

We actually don't need the macosx-cross toolchain to build compiler-rt,
because building compiler-rt doesn't require compiler-rt (duh).

Differential Revision: https://phabricator.services.mozilla.com/D101077

taskcluster/ci/toolchain/misc.yml

@@ -374,5 +374,5 @@ macosx64-aarch64-compiler-rt-11:
             - clang-11
         toolchain:
             - linux64-cctools-port-clang-11
-            - linux64-clang-11-macosx-cross
+            - linux64-clang-11
             - macosx64-sdk-11.0