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

[via llvm-commits]

thetruestblue wrote:

> The point was to try to reduce the special case paths. If there is a specific reason that we cannot treat AppleClang as we do the other compiles (i.e. pass through the identity unmodified), that would be good to document.

But this change "i.e. pass through the identity unmodified" is very new behavior added a month ago. And historically we matched any clang regex and set the compiler ID to Clang? This patch simply returns to a long standing assumption to avoid breaking tests.

Not changing this would require a special path in lit config (no big deal) but various Make files where we check that `(COMPILER_RT_TEST_COMPILER_ID MATCHES "Clang")`. Which, I'd argue is uglier.

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