[llvm] [offload] lazily load liboffload (PR #221731)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 commented:

Why does this need to be lazy? The status quo right now is that we initialize every plugin that's in the list the user provides to the `init` function's config struct. I would've assumed that we just move this step into `libomptarget`. We also really just need to get rid of the 'device initialization' concept.

https://github.com/llvm/llvm-project/pull/221731