Make QtQuickControls2 buildable without QtWidgets
requested to merge vkrause/craft-blueprints-kde:work/quickcontrols2-optional-widget-dependency into master
Usually that is achieved by not building QtWidgets at all, like we do for our Android packages currently. However, we do have libs/apps that need QAction, which is in QtWidgets in Qt 5 (moved to QtGui in Qt 6). With this patch we can still build QtWidgets but nevertheless avoid it being pulled into APKs that don't need it.
This does essentially the same 0ecec4d4 did for QtSvg.