can't build netboot image containing custom udebs

[Thiemo Nagel <thiemo.nagel@gmail.com>]

Hello debian-boot,

may I ask for your help with building a custom installer? After making
some modifications to partman-crypto, I'd like to build a mini.iso
image to test them. I've tried to follow instructions in

http://d-i.alioth.debian.org/doc/internals/ch04.html#id322221

but the desired udeb never shows up in tmp/netboot/udeb.list.

I've added partman-crypto to several of the files under pkg-lists, but
from the output of "make build_netboot" I've got the impression that
util/pkg-list isn't even called.

What am I doing wrong? Your help would be greatly appreciated!

Thank you and best regards,
Thiemo