[llvm] [OFFLOAD] Add support for host offloading device (PR #177307)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 commented:

I agree with this in principle, but I think the issue with turning on the host device is that launching 'kernels' on it doesn't work due to the fact that it uses `libffi`. I've tried many times to remove this dependency but was thwarted by OpenMP legacy I just didn't have the patience to deal with every step of the way. Honestly at this point I'd be open to making a branch in the host device like `isStupidOpenMPMode` and then handle it properly otherwise (Which is the same way pthreads handles things, AKA void * to struct and we just copy + pass the arguments.)

https://github.com/llvm/llvm-project/pull/177307