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

[Lakshay Kumar via llvm-commits]

lakshayk-nv wrote:

> LGTM (carrying over from the last patch).
> 
> Were you able to reproduce the issue locally?

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.

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