[llvm] [UTC] Support to test annotated IR (PR #165419)

[Alexander Richardson via llvm-commits]

https://github.com/arichardson commented:

Should this be the default behaviour (with a --version bump)?

Being able to use CHECK-NEXT more instead of the more fragile CHECK is IMO a good thing.

https://github.com/llvm/llvm-project/pull/165419