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

[David Green via cfe-commits]

davemgreen wrote:

It is that bit of code, yeah. I don't know of a way to reproduce this without logging into different machines with different sets of options and trying it.

If we had a way to test/mock that various /proc/cpuinfo files gave us the correct results, that would be helpful in giving us more confidence it was working as intended.

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