ROS workspace compilation problem: nvoking "cmake" failed

Problem Description:

CMake Error at CMakeLists.txt:1:
  Parse error.  Expected a command name, got unquoted argument with text
  "/opt/ros/melodic/share/catkin/cmake/toplevel.cmake".

-- Configuring incomplete, errors occurred!
Invoking "cmake" failed

Solution:
delete the CMakeLists.txt file under src, and re-catkin_init_workspace