How to add custom plugin to the cpack package

i have wrote one custom plugin , and i want the PACKAGE project can package the plugin
i try to write the cmake in cmake_install.cmake like this

it does true to package the custom plugin into the slicer project tree and running without error,but it can’t package into a exe file with the error below

i guess i wrote a wrong way , it should not wirte into the cmake_install.cmake file,but i don’t known which file should do the work.