[clang] [OpenMP] Prevent AMDGPU from overriding visibility on DT_nohost variables (PR #68264)

[Jon Chesterfield via cfe-commits]

https://github.com/JonChesterfield commented:

This stuff looks very cuda/opencl specific. It's definitely surprising for C++ code. Do we need it for openmp? If not it seems better to guard the hack with visibility behind if (hip)

https://github.com/llvm/llvm-project/pull/68264