move all our stuff into /lkmc in guest

Motivation: userland is getting several new subdirectories, it would be
too insane to just dump all of that in the guest root filesystem.

To alleviate the cd pain, .profile puts user inside /lkmc by default.

rootfs_overlay/lkmc/dep.sh

@@ -0,0 +1,27 @@
+#!/bin/sh
+set -e
+f=/sys/kernel/debug/lkmc_dep
+f2=/sys/kernel/debug/lkmc_dep2
+
+insmod dep.ko
+insmod dep2.ko
+
+# Initial value.
+[ "$(cat "$f")" = 0 ]
+
+# Changhing dep2 also changes dep.
+printf 1 > "$f2"
+[ "$(cat "$f")" = 1 ]
+
+# Changhing dep also changes dep2.
+printf 2 > "$f"
+[ "$(cat "$f2")" = 2 ]
+
+# sysfs shows us that the module has dependants.
+[ "$(cat /sys/module/dep/refcnt)" = 1 ]
+[ "$(ls /sys/module/dep/holders)" = dep2 ]
+rmmod dep2.ko
+[ "$(cat /sys/module/dep/refcnt)" = 0 ]
+[ -z "$(ls /sys/module/dep/holders)" ]
+
+rmmod dep.ko