Fix build with SKG_DESIGNER=OFF

Authored by asturmlechner on Sep 5 2018, 6:46 AM.

Description

Fix build with SKG_DESIGNER=OFF

Summary: cmake was adding designerplugin code to build with SKG_DESIGNER=OFF.

Reviewers: Skrooge, smankowski

Reviewed By: Skrooge, smankowski

Differential Revision: https://phabricator.kde.org/D15282

Details