[clang] [libc] [llvm] [openmp] [libc] Rework the GPU build to be a regular target (PR #81921)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

One large patch may be necessary - is it also necessary to interleave reordering files with changing the contents? It makes the GUI diff tool we're using here essentially useless. If the moving code between files and factoring into functions was a separate commit we'd have a much better chance of seeing what you've changed vs what you've moved.

https://github.com/llvm/llvm-project/pull/81921