[libunwind] [libunwind][AArch64] Protect PC within libunwind's context. (PR #113368)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

Sorry for the delay, now that we've got the qualifier and various other features upstreamed, I'll be upstreaming our ptrauth hardening for the various runtime libraries in the not too distant future (I'm technically on vacation this week, but it may go up this week, otherwise it should be up as a PR sometime next week)

https://github.com/llvm/llvm-project/pull/113368