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

[Nico Weber via cfe-commits]

nico wrote:

Looks like this breaks building on Android: https://ci.chromium.org/ui/p/chromium/builders/try/android-arm64-rel/680348/overview

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