I'm currently preparing one of my embedded system for a test-run and noticed 
that a *binary* package of media-libs/libpng pulls in the autofoo-stuff.

I went looking for the reason, looked into the eutils, multilib and finally 
autotools eclasses and saw that the autotools.eclass is setting the DEPEND 
but not the RDEPEND. IIRC portage-2.1 is now setting RDEPEND to DEPEND if 
nothing other is assigned within the ebuild/eclass.

So the simplest fix would be to assign RDEPEND="" in the eclass [1].

If no-one objects, I will commit the changes on monday.

TIA, Christian

1:http://dev.gentoo.org/~phreak/files/patches/autotools.eclass.diff

-- 
Christian Heim <phreak at gentoo.org>
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Your friendly mobile/kernel/vserver/openvz monkey