[clang] [llvm] [Driver][SYCL] Add initial SYCL offload compilation support (PR #107493)

[Alexey Bader via cfe-commits]

https://github.com/bader commented:

@mdtoguchi, thank you for working on this!
Overall, looks good to me, but I made a few suggestions in the comments.
It would be great if @tahonermann and @AaronBallman can confirm that all their comments are addressed.

https://github.com/llvm/llvm-project/pull/107493