Do not try to load plugin when building without decos

config-kwin.h.cmake

@@ -1,2 +1,3 @@
 /* Define if you have libcaptury */
 #cmakedefine HAVE_CAPTURY 1
+#cmakedefine KWIN_BUILD_DECORATIONS 1

plugins.cpp

@@ -20,6 +20,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 
 #include "plugins.h"
+#include "config-kwin.h"
 
 #include <kglobal.h>
 #include <klocale.h>
@@ -35,7 +36,11 @@ PluginMgr::PluginMgr()
 {
     defaultPlugin = (QPixmap::defaultDepth() > 8) ?
                     "kwin3_oxygen" : "kwin3_plastik";
+#ifdef KWIN_BUILD_DECORATIONS
     loadPlugin("");   // load the plugin specified in cfg file
+#else
+    setNoDecoration(true);
+#endif
 }
 
 void PluginMgr::error(const QString &error_msg)