Currently the portage tree contains pkgconfig version 0.8.0 which is too old for building e.g. gtk-2. Currently the newest stable version is 0.12.0, which seems to build fine and work without any problems on a gentoo system. To update the ebuild just rename it i.e. cp pkgconfig-0.8.0.ebuild pkgconfig-0.12.0.ebuild
Works for me too. Committed
db fix