dosfstools required for building images on Debian

[GreenReaper]

Just thought I'd mention for possible inclusion in the readme:

During the ./buildUEFI64 step, I got the following

+ sudo mkfs.vfat /dev/loop0 -n UEFI64
sudo: mkfs.vfat: command not found

Indeed, it was not there, and this was because dosfstools was not installed. Perhaps it is available in Ubuntu, but it might be worth adding it to the line with sudo apt install autoconf nasm anyway, as installing it manually if it's already there shouldn't hurt, while the error is otherwise easy to miss if running all commands at once.