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

[Jon Roelofs via llvm-commits]

jroelofs wrote:

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

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