Fixed OpenMP flags for hipcc

#

if( OPENMP_FOUND AND ${WITH_OPENMP} )

   set( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DHAVE_OPENMP ${OpenMP_CXX_FLAGS}" )

   set( HIP_HIPCC_FLAGS "${HIP_HIPCC_FLAGS} -DHAVE_OPENMP ${OpenMP_CXX_FLAGS}" )

   # OpenMP libraries have to be added explicitly for HIP

   # https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_STANDARD_LIBRARIES.html

   # FIXME: ${OpenMP_CXX_LIBRARIES} is a ;-list and does not contain "-l"

   #list( APPEND CMAKE_HIP_STANDARD_LIBRARIES ${OpenMP_CXX_LIBRARIES} )

   list( APPEND CMAKE_HIP_STANDARD_LIBRARIES "-lgomp -lpthread" )

   list( APPEND CMAKE_HIP_STANDARD_LIBRARIES "-lomp -lpthread" )

endif()

####