CMake Error at FileSetWrongSyntax.cmake:4 \(target_sources\):
  Cannot find source file:

    FILE_SET

  Tried extensions ([^
]+
)+
  Hint: the FILE_SET keyword may only appear after a visibility specifier or
  another FILE_SET within the target_sources\(\) command.
Call Stack \(most recent call first\):
  CMakeLists.txt:3 \(include\)