Properly handle loop device names when there are > 10 devices on the

system.

debian/changelog

@@ -1,6 +1,8 @@
 livecd-rootfs (2.479) UNRELEASED; urgency=medium
 
   * Purge initramfs-tools from minimized images.
+  * Properly handle loop device names when there are > 10 devices on the
+    system.
 
  -- Steve Langasek <steve.langasek@ubuntu.com>  Fri, 13 Oct 2017 17:14:58 -0400
 

live-build/functions

@@ -56,7 +56,7 @@ mount_image() {
 
     # Find the loop device
     loop_p1="$(echo -e ${kpartx_mapping} | head -n1 | awk '{print$3}')"
-    loop_device="/dev/loop$(echo ${loop_p1} | cut -b5)"
+    loop_device="/dev/${loop_p1%p[0-9]*}"
     if [ ! -b ${loop_device} ]; then
         echo "unable to find loop device for ${backing_img}"
         exit 1