This will generate a label ARCHISO_$randomstring using the pwgen
utility and add this label to the kernel command line.
A new label will be generated for each image, so it can be uniquely
identified.
Patch from brain0 <thomas@archlinux.org>

Signed-off-by: Gerhard Brauer <gerbra@archlinux.de>
Signed-off-by: Aaron Griffin <aaronmgriffin@gmail.com>