Fix missing var

gnome-shell/mk_patched_yaru_debs.sh

 #!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
 
 # Dépendances build
 apt install -y debhelper dh-migrations libgtk-3-dev git meson sassc