[llvm] [CI] Upload JUnit Test Results as Artifacts (PR #141905)

[David Spickett via llvm-commits]

DavidSpickett wrote:

I'm thinking of buildkite and that's done in the YAML file instead - https://github.com/llvm/llvm-project/blob/a7322d7948637aa45e9d86162601a97eb0ac2668/.ci/generate-buildkite-pipeline-premerge#L89.

https://github.com/llvm/llvm-project/pull/141905