[CUDA] "CL/sycl.hpp" include not found when compiling with CUDA backend

[cgleggett]

header CL/sycl.hpp is not automatically found when targeting the CUDA backend, unless the include directory is explicitly specified in the compilation line via -I$(SYCL_BLD_DIR)/include/sycl

This is not the case if the CUDA backend is not targeted.

[vladimirlaz]

Fix is available in #1347

[cgleggett]

looks good. I'm now faced with #1353, but it looks like it's finding the header files without manual intervention.

[bader]

Fixed by #1347.