[llvm] [OpenMP][offload] Add LIBOMPTARGET_KERNEL_EXE_TIME (PR #222105)

[Shilei Tian via llvm-commits]

https://github.com/shiltian commented:

I'd expect the interface to be like a plugin instead of baked directly into the language runtime. It needs to be a generic interface.

I'm not going to block this change, and I'll leave the decision to @jhuber6 and @jdoerfert.

https://github.com/llvm/llvm-project/pull/222105