Close the door so it latches, put your foot down right at the door, and push the door farther in. Measure the gap between your foot and the door at the new position. Trim a piece of wood to the height of the door frame and the width you measured earlier, rip off old weather stripping, attach wood however you see fit, apply new weather stripping.

I've never done this and I'm talking out my ass but I think it should work. Probably have to adjust your strike plates for the locks to latch and bolt properly afterword