Add hooks.sh for legacy usrpkgs

src/hooks.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+# This file is meant to maintain legacy support.
+
+printf "This package uses the legacy hooks file (/etc/glacier/hooks.sh).\n"
+printf ">>> This is not an error. <<< There is no manual intervention needed.\n"
+printf "If you are the maintainer of this package, please update your usrbuild.sh, usrupdate.sh, and usrremove.sh accordingly.\n"
+
+source /etc/glacier/hooks && /etc/glacier/hooks