fix(uffd-admin): Fix bug with util-linux fallback path

Use runuser instead of su, as su does not really support multiple arguments to -c

Fixes #112

debian/contrib/uffd-admin

@@ -9,8 +9,8 @@ if [ "$(whoami)" = "uffd" ]; then
 	flask "$@"
 elif command -v sudo &> /dev/null; then
 	exec sudo --preserve-env=FLASK_APP,CONFIG_FILENAME -u uffd flask "$@"
-elif command -v su &> /dev/null; then
-	exec su -s /bin/sh --preserve-environment uffd -c flask "$@"
+elif command -v runuser &> /dev/null; then
+	exec runuser --preserve-environment -u uffd -- flask "$@"
 else
 	echo "Could not not become 'uffd' user, exiting"
 	exit 255