[llvm] [Offload] Move `/openmp/libomptarget` to `/offload` (PR #75125)

[via llvm-commits]

dhruvachak wrote:

Thanks @jdoerfert 
Yes, I see that change now in offload/CMakeLists.txt. @jplehr Please verify you see the OMPT tests passing now in the buildbot.

https://github.com/llvm/llvm-project/pull/75125