[clang] [llvm] [Driver][SYCL] Add initial SYCL offload compilation support (PR #117268)

[Michael Toguchi via llvm-commits]

mdtoguchi wrote:

> also:
> 
> ```
> clang/lib/Driver/ToolChains/SYCL.h:27:17: warning: private field 'D' is not used [-Wunused-private-field]
> ```

@jroelofs, these should be addressed with https://github.com/llvm/llvm-project/pull/121822

https://github.com/llvm/llvm-project/pull/117268