LE uses it's own add-on system to install packages. APT is not supported. Fortunately you don't need APT or an install script for this project.
- install the "Raspberry Pi Tools" add-on (provides Python GPIO lib)
- create the folder /storage/.kodi/userdata/scripts
- insert this lines between line 4 and 5 of softshut.py:
- put softshut.py into /storage/.kodi/userdata/scripts
- create /storage/.config/autostart.sh with this content: