Convert `find_source_dir` in a `check_source_dir` rasing ArgumentTypeError amd simplify `add_to_plan`
Convert `find_source_dir` in a `check_source_dir` rasing ArgumentTypeError
amd simplify `add_to_plan`

naufraghi/qt-pyqt-sdk-builder,develersrl/qt-pyqt-sdk-builder,naufraghi/qt-pyqt-sdk-builder,develersrl/qt-pyqt-sdk-builder,develersrl/qt-pyqt-sdk-builder,zehome/qt-pyqt-sdk-builder,aurelien-rainone/qt-pyqt-sdk-builder,aurelien-rainone/qt-pyqt-sdk-builder,naufraghi/qt-pyqt-sdk-builder,zehome/qt-pyqt-sdk-builder,aurelien-rainone/qt-pyqt-sdk-builder,zehome/qt-pyqt-sdk-builder