update CreateAppImage script to be usable from build folders
update CreateAppImage script to be usable from build folders

this makes it more usable for non-ci users

fourtf/chatterino2,Cranken/chatterino2,hemirt/chatterino2,hemirt/chatterino2,hemirt/chatterino2,fourtf/chatterino2,Cranken/chatterino2,Cranken/chatterino2,hemirt/chatterino2,Cranken/chatterino2,fourtf/chatterino2