[llvm] [Offload][WIP] Move `/openmp/libomptarget` to `/offload` (PR #82459)

[Jan Patrick Lehr via llvm-commits]

jplehr wrote:

> @jplehr I'm helping @jdoerfert with this PR. I added a fix that should hopefully fix the build error you were seeing previously (I recreated it on my machines too). Let me know any other problems you encounter and I'll fix them as they come!

Hey, good news. Thanks for working on that. I will see that I find some time in the near future to give it another try.

https://github.com/llvm/llvm-project/pull/82459