[libunwind] [llvm] [AArch64] Add .cfi_non_hint_pauth_frame when PAuth_LR instructions used for signing (PR #233885)

[Kerry McLaughlin via cfe-commits]

kmclaughlin-arm wrote:

> ABI-wise, I think you might also need to add a bit to the `UNW_AARCH64_RA_SIGN_STATE` pseudo register to describe this state, otherwise consumers of `_Unwind_GetGR(ctx, UNW_AARCH64_LR)` are unable to aut the value themselves, and must strip it.

This isn't an area that I am very familiar with, but are you saying that `_Unwind_GetGR` could be used outside of libunwind to try and recover the return address? If so, I think this is also a problem for how we distinguish whether the A or B key was used for signing, which is also recorded as a character in the augmentation string.

https://github.com/llvm/llvm-project/pull/233885