[SYCL] Don't include OpenCL headers when compiling for device

[uditagarwal97]

IGC wants the ability to compile SYCL device code and they don't have OpenCL headers installed. OpenCL headers are anyway not used when compiling for device.

[adamfidel]

Graph test LGTM

[uditagarwal97]

@intel/unified-runtime-reviewers-level-zero @intel/llvm-reviewers-runtime @againull ping

[koparasy]

@uditagarwal97 Customers who relied on sycl.hpp transitively pulling in <CL/cl.h> etc. will get compile time errors.

I have deleted till now a couple of transitive headers and usually (because of downstream regressions who start filling tickets) I come back and add an inclusion here.

No strong opinions here though.

[uditagarwal97]

@uditagarwal97 Customers who relied on sycl.hpp transitively pulling in <CL/cl.h> etc. will get compile time errors.

I have deleted till now a couple of transitive headers and usually (because of downstream regressions who start filling tickets) I come back and add an inclusion here.

No strong opinions here though.

@koparasy I agree, that's why several E2E tests are failing, because they were relying on SYCL headers to bring in OpenCL ones. With that said, SYCL Spec doesn't require us to provide OpenCL headers, and only those customers that uses OpenCL types, functions in their applications but relying on SYCL headers to pull in OpenCL ones will be affected.
The impact is limited IMO.