[clang] [FMV][AArch64][clang] Emit fmv-features metadata in LLVM IR. (PR #118544)

[Jon Roelofs via cfe-commits]

https://github.com/jroelofs approved this pull request.

The patch itself LGTM though, despite my gripes on the current prioritization rule.

https://github.com/llvm/llvm-project/pull/118544