[Darwin][CompilerRT] Set compiler ID to 'Clang' for Compiler RT Tests for Apple Clang (#121858)
This patch restores previous behavior. Even when the Compiler ID is set
to AppleClang, we expect Compiler RT Tests to use Clang as the compiler
ID. This impacts various make and lit commands.
Caused by: https://github.com/llvm/llvm-project/pull/117812/files
rdar://141548700