CLONE - Qt Creator UI does not adapt to high resolution displays (on Linux)

When running Qt Creator on a high resolution display (aka Retina Display), most of the UI elements do not adjust their size to the high DPI values. While some fonts adjust themselves nicely, others completely ignore the DPI settings and look very tiny. In some cases, the fonts adjust, but the containing buttons do not and the texts don't fit on the buttons any more. See the attached screenshots for details.