[arch-releng] pacman.conf.{i686,x86_64} ignored by archiso?

[Dieter Plaetinck]

in the releng env
(http://projects.archlinux.org/users/dieter/releng.git/tree/) it seems the
pacman.conf.{i686,x86_64} files are now being ignored. (i enabled testing in there but it's not used)
Frankly I don't even know/remember how this ever worked, I can't find a reference to these files anywhere.
How does one control which pacman.conf archiso must use during building of the arch environment it puts on the isos?

Dieter