[libunwind] [libunwind][PAC] Defang ptrauth's PC in valid CFI range abort (PR #184041)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

> `stripped_value` will be unused variable in the release builds, I guess. By the way, another option could probably be simply wrapping this fragment with `#ifndef _NDEBUG`? Though, I'm not sure whether we do want to skip authentication even in the debug builds or was `ptrauth_auth_and_resign` replaced with `ptrauth_strip` merely for the sake of performance in the release builds (which should not be a problem anymore with `#ifndef _NDEBUG`).

Oh oops, I just restored the old assertion logic but completely forgot that - I only built debug because that's my usual logic

https://github.com/llvm/llvm-project/pull/184041