[libunwind] [libunwind] Add GCS support for AArch64 (PR #99335)

[Tobias Hieta via cfe-commits]

tru wrote:

> Though having said all this, I marked this for LLVM 19 as my reading of https://discourse.llvm.org/t/update-on-llvm-19-x-releases/80511 was that new features are still ok before RC2, but re-reading it it's a bit ambiguous: it says "New features will have to wait until LLVM 20 at this point" and my reading of that was that "this point" means RC2, so new features before RC2 is fine, but if "this point" meant "right now" that means new features aren't OK. If that's the case the it's reasonable for this to not go in RC2.

I am fine with it going into RC2 if it's part of a on-going work as you explained and that it doesn't create any big issues. Unfortunately with nico's latest comment it seems like this is breaking some build configurations and I am cutting RC2 now, I don't feel comfortable to merge it before that has been investigated. I can probably be convinced to take it in RC3 if it's really helpful to do so and it have been working without any problems.

https://github.com/llvm/llvm-project/pull/99335