Support empty sources in add_executable and add_library
Support empty sources in add_executable and add_library

Change-Id: I1441f2c045aeda2bba99bffe1c99fcc4a59cea9b

ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP,ROCm-Developer-Tools/HIP