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

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

Given that it's been a week, I'm merging; if @MaskRay has any concerns, they can be addressed post commit.

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