FindOpenMP: Add support for HIP clang device pass.
The HIP clang makes 2 passes when compiling HIP programs: the DEVICE pass and the HOST pass. For openmp, the
-fopenmp option is only passed to the HOST compilation pass. Therefore, the small test that CMake uses for OpenMP detection fails to compile, and CMake reports failure to detect OpenMP support in the compiler. The suggested solution is to add check for
__HIP_DEVICE_COMPILE__ macro defined by HIP clang for the DEVICE pass to the OpenMP detection test.