[QGIS-Developer] Again qgis_customwidgets and Qt Designer

[Matteo Ghetta]

Thanks Calvin for checking.

The workaround (Linux debian) I found is copying the files of the
output/lib directory (libqgis_customwidgets.so and
libqgis_customwidgets.so.3.5.0) manually in
/usr/lib/x86_64-linux-gnu/qt5/plugins/designer and removing the old
files within this directory.

After this manual copy I can see them in Designer.

Cheers

Matteo