Add post update script and service

etc/systemd/system/post-update.service

@@ -0,0 +1,11 @@
+[Unit]
+Description=Post Deck update configuration
+Requires=network-online.target
+After=network-online.target
+
+[Service]
+Type=oneshot
+ExecStart=/etc/systemd/system/post-update.sh
+
+[Install]
+WantedBy=multi-user.target

etc/systemd/system/post-update.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+if [ ! -f /post-update-done ]; then
+    steamos-readonly disable
+    pacman-key --init
+    pacman-key --populate archlinux
+    pacman -S --noconfirm glibc
+    sed -i 's/#\(ja_JP.UTF-8.*\)/\1/' /etc/locale.gen
+    locale-gen
+    touch /post-update-done
+    steamos-readonly enable
+fi