[llvm] [llvm-exegesis][AArch64] Check for PAC keys before disabling them (PR #138643)

[Anatoly Trosinenko via llvm-commits]

https://github.com/atrosinenko commented:

@abhilash1910 Thanks for the updates, I left a few comments on `prctl_wrapper` so far, will re-test the patch in QEMU slightly later.

https://github.com/llvm/llvm-project/pull/138643