[clang] [flang] [llvm] [openmp] [Flang] Move builtin .mod generation into runtimes (Reapply #137828) (PR #169638)

[Joseph Huber via llvm-commits]

jhuber6 wrote:

One problem with enabling flang-rt on the GPU is that it has a dependency on libc / libc++ on the GPU as well. Maybe there's a way to make it work there just to build the module files?

https://github.com/llvm/llvm-project/pull/169638