Make it actually non-bash dependent

changed the way script_dir is found to not call on bash

Author: OrioleNix

scripts/APPIMAGE_INSTALL.sh

@@ -4,7 +4,7 @@
 set -e
 
 # Move to script's directory
-SCRIPT_DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
 cd "${SCRIPT_DIR}"
 
 #add .desktop file (which should allow most DE's easy access to the program