[clang] [AArch64] Add getHostCPUFeatures to query for enabled features in cpu… (PR #97749)

[David Green via cfe-commits]

davemgreen wrote:

Hi this sounds like a good idea to me. Note that the implementation of getHostCPUFeatures isn't amazing for AArch64 at the moment, there was an attempt to fix it up in #95694 (but thaat has gone a bit quiet). One point we noticed is that it could end up turning "aes+sha2" into "crypto" and "crypto" back into "sha2+aes+sha3+sm4", as it uses the old meaning of "crypto"

https://github.com/llvm/llvm-project/pull/97749