[llvm] [llvm-exegesis][AArch64] Disable pauth and ldgm as unsupported instructions fixed (PR #136868)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

> Yes, We replicated build failure locally using a x86_64 machine with Ubuntu 20.04.6 LTS. And reproduced build failure `error: ‘PR_PAC_SET_ENABLED_KEYS’ was not declared in this scope.

Sounds good. Seems perfectly reasonable to reland then.

https://github.com/llvm/llvm-project/pull/136868