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

[via llvm-commits]

thetruestblue wrote:

> I'd prefer to do the canonicalization at the end of this if-else chain for future proofing, i.e

I'm fine with this. Thanks very much! 

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