Create fs-overlay, post-build

Setup buildroot filesystem overlay and move our custom scripts/configs
into it.  Setup a post-build script and have it delete files generated
by buildroot that aren't in RescueOS v1.1.

This gets us closer to a buildroot configuration that will automatically
generate RescueOS images.  For now, we're using RescueOS v1.1 as a
reference.

fs-overlay/usr/share/udhcpc/default.script

@@ -0,0 +1,48 @@
+#!/bin/sh
+# udhcpc script edited by Tim Riker <Tim@Rikers.org>
+
+RESOLV_CONF="/etc/resolv.conf"
+
+[ -n "$1" ] || { echo "Error: should be called from udhcpc"; exit 1; }
+
+NETMASK=""
+[ -n "$subnet" ] && NETMASK="netmask $subnet"
+BROADCAST="broadcast +"
+[ -n "$broadcast" ] && BROADCAST="broadcast $broadcast"
+
+case "$1" in
+	deconfig)
+		echo "Setting IP address 0.0.0.0 on $interface"
+		ifconfig $interface 0.0.0.0
+		;;
+
+	renew|bound)
+		echo "Setting IP address $ip on $interface"
+		ifconfig $interface $ip $NETMASK $BROADCAST
+
+		if [ -n "$router" ] ; then
+			echo "Deleting routers"
+			while route del default gw 0.0.0.0 dev $interface ; do
+				:
+			done
+
+			metric=0
+			for i in $router ; do
+				echo "Adding router $i"
+				route add default gw $i dev $interface metric $((metric++))
+			done
+		fi
+
+		echo "Recreating $RESOLV_CONF"
+		echo -n > $RESOLV_CONF-$$
+		[ -n "$domain" ] && echo "search $domain" >> $RESOLV_CONF-$$
+		for i in $dns ; do
+			echo " Adding DNS server $i"
+			echo "nameserver $i" >> $RESOLV_CONF-$$
+		done
+		mv $RESOLV_CONF-$$ $RESOLV_CONF
+		;;
+esac
+
+exit 0
+