[clang] [llvm] [Libomptarget] Statically link all plugin runtimes (PR #87009)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> I did not build upstream but looking at downstream, I think for some reason they don't show up as duplicate symbols. But looking at the code, they should be removed. There are uses of those variables in the plugin, so there should be only 1 definition.

Does this apply for anything OMPT related inside of the plugin? There's a few places where we mark callbacks, but those can all be moved into `libomptarget` once this lands.

https://github.com/llvm/llvm-project/pull/87009