[llvm] Change check for embedded llvm version number to a regex to make test more flexible. (PR #79528)

[Tom Stellard via llvm-commits]

tstellar wrote:

> @tstellar what is the process for getting commits included on the release branch? Should I open another PR with this change against the release/18.x branch?

Yes, you can do that.

https://github.com/llvm/llvm-project/pull/79528