[llvm] [MachineVerifier] Report errors from one thread at a time (PR #111605)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

Probably fine, but I don't think we really need the verifier to be thread safe. Step 1 of debugging any issue would be to get a standalone reproducer which fails 

https://github.com/llvm/llvm-project/pull/111605