[clang] [llvm] [ci] Write test results to unique file names (PR #113160)

[David Spickett via cfe-commits]

DavidSpickett wrote:

You can see the new artifacts here: https://buildkite.com/llvm-project/github-pull-requests/builds/111782#0192af36-eae5-4676-b226-f6cf98fc1083

Just rebased to maybe get a clean Windows build, I think the failure there is due to the newline policy changes recently.

https://github.com/llvm/llvm-project/pull/113160