[llvm] [openmp] [OpenMP] Change build of OpenMP device runtime to be a separate runtime (PR #136729)

[Michał Górny via llvm-commits]

mgorny wrote:

I've filed #151930 as a possible workaround. If that is merged and doesn't cause any regressions, I can look at the other issues — such as broken search for test dependencies.

https://github.com/llvm/llvm-project/pull/136729