[compiler-rt] [Darwin][CompilerRT] Set compiler ID to 'Clang' for Compiler RT Tests for Apple Clang (PR #121858)

[Alexander Richardson via llvm-commits]

https://github.com/arichardson requested changes to this pull request.

I just looked and there are only 3 uses comparing compiler_id to "Clang", all of them in `lit.common.cfg.py`. I think we can just change those to also accept AppleClang (or use .endswith())?

https://github.com/llvm/llvm-project/pull/121858