[llvm] [Offload] Add OFFLOAD_FORCE_SYNC_OPS force-synchronization escape hatch (PR #222635)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 commented:

Doesn't CUDA have some environment variable for like CUDA_BLOCKING or something? Is that similar to this?

https://github.com/llvm/llvm-project/pull/222635