[llvm] [BOLT][NFC] Add MCPlusBuilder unittests for PAuth helpers (PR #162251)

[Gergely Bálint via llvm-commits]

bgergely0 wrote:

Hmm, not sure what the failure in the auto-subscribe job is. This is my first PR from a user branch, could be related?

https://github.com/llvm/llvm-project/pull/162251