[llvm] Normalize file path to fix problems with different folder separators. (PR #215225)

[James Henderson via llvm-commits]

jh7370 wrote:

> Two checks are failing, but it doesn't seem to be related with the change itself.

Sorry for the delay. I've had some time off recently. You could try fixing the tests by merging in the latest main via a merge commit.

https://github.com/llvm/llvm-project/pull/215225