GNAP doesn write the portage_confdir settings when building extensions.
Created attachment 86932 [details, diff] grp_portage.patch
Nice one, this bug fix saved the day for me :-)
The GNAP project has been discontinued, its removal was acknowledged by steev. If you need to, you can contact the Gentoo Embedded project; more information about the Gentoo Embedded project can be found on the following link: http://www.gentoo.org/proj/en/base/embedded/ This removal happens as part of project cleanup by the Gentoo Council's members.