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

[via cfe-commits]

asmok-g wrote:

Hello, 

This patch makes the following line fail to compile
```
#elif ABSL_HAVE_BUILTIN(__builtin_cpu_supports)
  if (__builtin_cpu_supports("avx2")) {
```

`error: invalid cpu feature string for builtin` when built on arm

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