patching with `xdelta` resolves in wrong error while `xdelta3` works

[carafelix]

first, I installed xdelta and run build_linux_and_mac.sh game.iso with the following iso, md5sum: 0e63d4223b01d9aba596259dc155a174 game.iso

and got: ERROR: The ISO 'game.iso' is not a valid v1.02 NTSC melee iso

same iso but installed xdelta3 and it worked.

something ain't checking ok with xdelta