Add a switch_root utility (like kconfig's utils/run_init.c, although not
actuall using any of that code).  This is needed because pivot_root doesn't
work right under initramfs.  (See the menuconfig help.)
diff --git a/include/applets.h b/include/applets.h
index a814ce1..883e559 100644
--- a/include/applets.h
+++ b/include/applets.h
@@ -625,6 +625,9 @@
 #ifdef CONFIG_SWAPONOFF
 	APPLET(swapon, swap_on_off_main, _BB_DIR_SBIN, _BB_SUID_NEVER)
 #endif
+#ifdef CONFIG_SWITCH_ROOT
+	APPLET(switch_root, switch_root_main, _BB_DIR_SBIN, _BB_SUID_NEVER)
+#endif
 #ifdef CONFIG_SYNC
 	APPLET(sync, sync_main, _BB_DIR_BIN, _BB_SUID_NEVER)
 #endif