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.

buildrootconfig

@@ -11,6 +11,8 @@ BR2_TARGET_GENERIC_HOSTNAME="rescueos"
 BR2_TARGET_GENERIC_ISSUE="Welcome to RescueOS"
 BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_DEVTMPFS=y
 # BR2_TARGET_GENERIC_REMOUNT_ROOTFS_RW is not set
+BR2_ROOTFS_OVERLAY="../N900_RescueOS/fs-overlay"
+BR2_ROOTFS_POST_BUILD_SCRIPT="../N900_RescueOS/post-build.sh"
 BR2_PACKAGE_BUSYBOX_CONFIG="../N900_RescueOS/busyboxconfig"
 BR2_PACKAGE_BUSYBOX_SHOW_OTHERS=y
 BR2_PACKAGE_TAR=y

etc/fstab

@@ -1,9 +0,0 @@
-# /etc/fstab: static file system information.
-#
-# <file system> <mount pt>     <type>	<options>         <dump> <pass>
-/dev/root       /              ext2	rw,noauto         0      1
-proc		/proc	       proc     defaults	  0	 0
-devpts		/dev/pts       devpts   defaults,gid=5,mode=620	  0	 0
-tmpfs           /dev/shm       tmpfs    mode=0777         0      0
-tmpfs           /tmp           tmpfs    defaults          0      0
-sysfs		/sys	       sysfs    defaults	  0	 0

etc/hostname

@@ -1 +0,0 @@
-rescueos

etc/passwd-

@@ -1 +0,0 @@
-root:$1$6WxBQ9E9$xc/J67N0/3N1HAsGkVur..:0:0:root:/root:/bin/bash

fs-overlay/etc/resolv.conf

@@ -0,0 +1 @@
+/run/resolv.conf

post-build.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+set -e
+
+target="$1"
+
+delfiles=" \
+  $target/etc/init.d/rcK \
+  $target/etc/init.d/S20urandom \
+  $target/etc/init.d/S40network \
+  $target/etc/securetty"
+for file in $delfiles ; do 
+  [ -e "$file" ] && rm "$file" || true
+done