Add kernel config update helper

update_config.sh

+#!/bin/bash
+
+[[ -e src/linux/.config ]] || makepkg --nobuild --force
+
+(cd src/linux && make oldconfig)
+
+if ! diff -q -s src/linux/.config config.x86_64; then
+	cp src/linux/.config config.x86_64
+	updpkgsums
+fi