[llvm] llc: Verify MIR outputs by default (PR #228248)

[Arthur Eubanks via llvm-commits]

https://github.com/aeubanks commented:

things seem cleaner if we have some overarching VerifyType enum with values like `None`, `Each`, `BeginAndEnd`. there are a lot of confusing conditionals here

https://github.com/llvm/llvm-project/pull/228248