message: interop example is CUDA-only
  Although it doesn't need to be.. should probably port this to C++, too
diff: @@ -49,7 +49,9 @@ add_subdirectory(juggler)
  #add_subdirectory(minimal)
  #add_subdirectory(multi_hit)
  add_subdirectory(multi_volume)
  +if (VSNRAY_ENABLE_CUDA AND CUDA_FOUND)
  add_subdirectory(opengl_interop)
  +endif()
  add_subdirectory(phantom)
  add_subdirectory(raytracinginoneweekend)
  if (VSNRAY_ENABLE_CUDA AND CUDA_FOUND)
  