Comment 7 for bug 1679252

This does fix the issue for arm64 (where I tested the patch), but ppc64el and powerpc need an additional change:

=== modified file 'live-build/ubuntu-cpc/hooks/034-disk-image-ppc64el.binary'
--- live-build/ubuntu-cpc/hooks/034-disk-image-ppc64el.binary 2016-04-14 18:06:33 +0000
+++ live-build/ubuntu-cpc/hooks/034-disk-image-ppc64el.binary 2016-06-09 14:48:38 +0000
@@ -26,6 +26,7 @@
     mkdir mountpoint
     mount_partition "${rootfs_dev_mapper}" mountpoint

+ chroot mountpoint apt-get -qqy update
     chroot mountpoint apt-get -qqy install grub2
     chroot mountpoint apt-get -qqy remove --purge grub-legacy-ec2