[llvm] Revert "[Offload] Run unit tests as a part of check-offload" (PR #157346)

[Joseph Huber via llvm-commits]

jhuber6 wrote:

Also while we're here, I'd like to delete the current standalone build and replace it with the runtimes build. The one where you do `cmake ../runtimes -DLLVM_ENABLE_RUNTIMES=offload`. Is that something we could move towards?

https://github.com/llvm/llvm-project/pull/157346