[llvm] [TableGen] Allow disabling flag checking on patterns (PR #176443)

[Jay Foad via llvm-commits]

jayfoad wrote:

I tend to agree that there's probably no way to make the checks rigorous. I guess we could turn them into a warning that's off by default (similar to the globalisel backend's -warn-on-skipped-patterns), but then maybe no-one would ever bother to enable the warning and the checking code would rot.

https://github.com/llvm/llvm-project/pull/176443