[compiler-rt] [CMake] [compiler-rt] fix architecture checks in runtime builds (PR #66374)

[Petr Hosek via llvm-commits]

petrhosek wrote:

Have you tried using `COMPILER_RT_DEFAULT_TARGET_ONLY`? The `test_target_arch` macro is used in `test_targets` which has a number of issues and ideally we should try to remove it altogether.

https://github.com/llvm/llvm-project/pull/66374