The QmlDesigner plugin can no longer run without Project Storage
support.
It remains buildable for the Qt Creator use case, but brings up a warning.
In the BUILD_DESIGNSTUDIO case, CMake emits a fatal configuration error.
Change-Id: Ic2a62e27eea6cd1327d8a3c1397e25ca55ad1e39
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>