[clang] [compiler-rt] [AArch64] Implement __builtin_cpu_supports, compiler-rt tests. (PR #82378)

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alexfh wrote:

This makes the clang diverge from the GCC behavior, for example, GCC happily compiles `(void)__builtin_cpu_supports("neon");` on x86, but clang doesn't after this patch: https://gcc.godbolt.org/z/a367Pd7sE

https://github.com/llvm/llvm-project/pull/82378