Ubuntu 16.10 creates unbootable device when using flash.sh

mkfs creates ext4 volumes with “Filesystem features” that include ‘64bit’.

The bootloader does not really like this and fails to boot as a result.

replacing a line in flash.sh from:

mkfs -t $4 "${loop_dev}" > /dev/null 2>&1;

to:

mkfs -t $4 -O ^64bit,^metadata_csum "${loop_dev}" > /dev/null 2>&1;

fixes the issue for me