[kde-linux] Cmake build error for qPixmap stuff

[David Baron]

Lines like this from ui_myproject.h:

icon.addPixmap(QPixmap(qPixmapFromMimeSource(":/icons/audio-headset.xpm")), 
QIcon::Normal, QIcon::Off);

produce missing libraries on build:
... undefined reference to `qPixmapFromMimeSource(QString const&)

What do I need to add to my cmake to get this?

(Without it, I cannot get any icons into the widgets! Direct setIcon(QIcon( 
"....xpm") ) is an immediate crash.)