[libunwind] [libunwind] Call `__arm_za_disable` before entering EH (PR #160905)

[Sander de Smalen via cfe-commits]

https://github.com/sdesmalen-arm commented:

I'll leave it to code-owners/maintainers of libunwind to review or approve the PR further, but from an AArch64/SME point of view the change looks right to me.

https://github.com/llvm/llvm-project/pull/160905