[SYCL] Fix CUDA interop self-contained-headers test

[npmiller]

This header needs a sepcific macro to be defined when it is included which is why the generic test gives out warnings. Add a specific test for it so we can define the macro.

[aelovikov-intel]

Is that because of

llvm/sycl/include/sycl/backend.hpp

Lines 208 to 221 in ce5bfa8

	#ifndef SYCL_EXT_ONEAPI_BACKEND_CUDA_EXPERIMENTAL
	template <>
	__SYCL_DEPRECATED(
	"Context interop is deprecated for CUDA. If a native context is required,"
	" use cuDevicePrimaryCtxRetain with a native device")
	inline backend_return_t<backend::ext_oneapi_cuda, context> get_native<
	backend::ext_oneapi_cuda, context>(const context &Obj) {
	if (Obj.get_backend() != backend::ext_oneapi_cuda) {
	throw sycl::exception(make_error_code(errc::backend_mismatch),
	"Backends mismatch");
	}
	return reinterpret_cast<backend_return_t<backend::ext_oneapi_cuda, context>>(
	Obj.getNative());
	}

? I don't see why it matters...

https://github.com/search?q=repo%3Aintel%2Fllvm%20SYCL_EXT_ONEAPI_BACKEND_CUDA_EXPERIMENTAL&type=code doesn't show any other uses of the macro in the code...

[npmiller]

This is the more consequential use:

llvm/sycl/include/sycl/backend.hpp

Lines 34 to 40 in ce5bfa8

	#if SYCL_EXT_ONEAPI_BACKEND_CUDA
	#ifdef SYCL_EXT_ONEAPI_BACKEND_CUDA_EXPERIMENTAL
	#include <sycl/ext/oneapi/experimental/backend/backend_traits_cuda.hpp>
	#else
	#include <sycl/detail/backend_traits_cuda.hpp>
	#endif
	#endif

There's different backend traits depending on which version of the interop is used. The experimental header doesn't work with the legacy traits, and it can't all be contained to the header because the SYCL headers need to know about the type traits as well. This is extremely clunky and needs to be cleared up eventually so we only have one set of interop traits, but that's how it works at the moment.

[npmiller]

@intel/llvm-gatekeepers this looks good to merge.

The PVC failure looks like there's an issue with the machine (can't find GPU), and this patch only changes a compiler only test, so it shouldn't affect the PVC E2E results.

[sarnex]

I'm fixing the PVC machine now, yeah it's unrelated