kdesignerplugin: propagate qttools build input

pkgs/development/libraries/kde-frameworks/kdesignerplugin.nix

···
   nativeBuildInputs = [ extra-cmake-modules kdoctools ];
   buildInputs = [
     kcompletion kconfig kconfigwidgets kcoreaddons kiconthemes kio kitemviews
-    kplotting ktextwidgets kwidgetsaddons kxmlgui qttools sonnet
+    kplotting ktextwidgets kwidgetsaddons kxmlgui sonnet
   ];
+  propagatedBuildInputs = [ qttools ];
 }