mkdir must not fail.

debian/changelog

@@ -1,3 +1,9 @@
+livecd-rootfs (2.441~mtrudel2) zesty; urgency=medium
+
+  * 
+
+ -- Mathieu Trudel-Lapierre <cyphermox@ubuntu.com>  Thu, 23 Mar 2017 16:20:16 -0400
+
 livecd-rootfs (2.440) zesty; urgency=medium
 
   [ Steve Langasek ]

live-build/ubuntu-server-next/hooks/032-installer-squashfs.binary

@@ -26,7 +26,7 @@ fi
 SQUASH_ROOT=binary/boot/squashfs.dir
 OVERLAY_ROOT=binary/boot/overlay.dir
 
-mkdir "$OVERLAY_ROOT"
+mkdir -p "$OVERLAY_ROOT"
 
 setup_mountpoint binary/boot/squashfs.dir