Include Qt designer plugin
Description:
When a developer is working on main FreeCAD or some external workbench it's very helpful to have the FreeCAD's custom Qt widgets installed. In the FreeCAD Wiki there are instructions for users to compile themselves the Qt designer plugin shared library and add it to Qt path, since this package already includes other FreeCAD tools as fcinfo
or freecad-thumbnailer
I think it's a good idea to also include this plugin.
This is specially needed when you are creating a preferences page for your external workbench, otherwise using Qt widgets no data will be saved.
cd freecad-source/src/Tools/plugins/widget
qmake plugin.pro
make
cp libFreeCAD_widgets.so /usr/lib/qt/plugins/designer/