[llvm] [FileCheck] Allow -check-prefix to take multiple prefixes (PR #178187)

[James Henderson via llvm-commits]

jh7370 wrote:

I've not looked at the implementation, but +1 to the idea. I do think it should be mentioned in the release notes and probably on the Discourse forum too, otherwise people who are pedants like me might continue to "correct" people to use --check-prefix for single prefix sets, for consistency.

https://github.com/llvm/llvm-project/pull/178187