First call readlink on argument 0 and then dirname (#110)

Fixes support for being executed via a symbolic link.

Author: mxmlnkn

resources/AppRun.sh

@@ -2,7 +2,7 @@
 
 set -e
 
-this_dir="$(readlink -f "$(dirname "$0")")"
+this_dir="$(dirname -- "$(readlink -f -- "$0")")"
 
 # make appimagetool prefer the bundled mksquashfs
 export PATH="$this_dir"/usr/bin:"$PATH"