live-build/ubuntu-cpc/functions: mount tmpfs on /var/cache/apt and

/var/lib/apt, so we don't have to leave empty space in our derivative
images for packages that have been downloaded/installed/removed.  This
normally isn't relevant for the installed system, since the root
filesystem will auto-expand in place on the target disk, but lets us
ship smaller images.

debian/changelog

@@ -4,6 +4,14 @@ livecd-rootfs (2.408.15) UNRELEASED; urgency=medium
   * Drop preloading of grub modules that are built into the grub signed
     image.  This is functionally a no-op, changed only to clean up the code.
 
+  [ Steve Langasek ]
+  * live-build/ubuntu-cpc/functions: mount tmpfs on /var/cache/apt and
+    /var/lib/apt, so we don't have to leave empty space in our derivative
+    images for packages that have been downloaded/installed/removed.  This
+    normally isn't relevant for the installed system, since the root
+    filesystem will auto-expand in place on the target disk, but lets us
+    ship smaller images.
+
  -- Steve Langasek <steve.langasek@ubuntu.com>  Wed, 23 Aug 2017 17:35:40 -0700
 
 livecd-rootfs (2.408.14) xenial; urgency=medium

live-build/ubuntu-cpc/functions

@@ -87,6 +87,8 @@ setup_mountpoint() {
     mount proc-live -t proc "$mountpoint/proc"
     mount sysfs-live -t sysfs "$mountpoint/sys"
     mount -t tmpfs none "$mountpoint/tmp"
+    mount -t tmpfs none "$mountpoint/var/lib/apt"
+    mount -t tmpfs none "$mountpoint/var/cache/apt"
     mv "$mountpoint/etc/resolv.conf" resolv.conf.tmp
     cp /etc/resolv.conf "$mountpoint/etc/resolv.conf"
 
@@ -134,7 +136,7 @@ umount_settle() {
 umount_partition() {
     local mountpoint=${1}
     mv resolv.conf.tmp "$mountpoint/etc/resolv.conf"
-    for submnt in proc sys dev/pts dev tmp;
+    for submnt in var/cache/apt var/lib/apt proc sys dev/pts dev tmp;
     do
         umount_settle $mountpoint/$submnt
     done