CMake Error at /opt/ros/melodic/share/catkin/cmake/assert.cmake:20 (message)

buntu18.04编译时出现如下错误：

CMake Error at /opt/ros/melodic/share/catkin/cmake/assert.cmake:20 (message):
  

  Assertion failed: file '/usr/lib/arm-linux-gnueabihf/librt.so' does not
  exist.  Message: RT Library

解决方法：
进入到：/opt/ros/melodic/share/catkin/cmake/tools/rt.cmake文件
将if(NOT (APPLE OR WIN32 OR MINGW OR ANDROID))改为if(NOT (APPLE OR WIN32 OR MINGW OR ANDROID OR UNIX))
然后，重新编译