[llvm] [mlir][spirv] Add mlir-spirv-tests CI to run for mlir-spv target tests (PR #152124)

[Jakub Kuderski via llvm-commits]

kuhar wrote:

I'm going to merge once we confirm that the new check works as intended: https://github.com/llvm/llvm-project/actions/runs/16807047739/job/47602153053?pr=152124 

https://github.com/llvm/llvm-project/pull/152124