[llvm] [BOLT] Add GNUPropertyRewriter and warn on AArch64 BTI note (PR #161206)

[Paschalis Mpeis via llvm-commits]

https://github.com/paschalis-mpeis approved this pull request.

Hey Gergely,

Thanks for adding support for reading features from `.note.gnu.property`.
I added a few nits.

https://github.com/llvm/llvm-project/pull/161206