[clang] clang/OpenCL: Add baseline test showing broken codegen (PR #138862)

[Matt Arsenault via cfe-commits]

arsenm wrote:

### Merge activity

* **May 8, 1:36 AM EDT**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/138862).


https://github.com/llvm/llvm-project/pull/138862