You need a proper impact driver ideally with the right sized bit.
If thats no good get a small chisel and drift the bu88ers out.
Remember to use copper slip and don't tighten the new ones up too much so you can get them out next time.
If all of this is no good you will have to drill the buggers out. you may find that by taking the head of the screw off it may loosen it up enough to remove it.
If the worst comes to the worst once you have drilled out don't bother refiting the screws, they don't really do anything as the studs and wheel nuts hold the discs in place.