Please add the following line to the ebuild, in order to restrict binary distribution with USE=-bindist: RESTRICT="!bindist? ( bindist )"
Please hold on, because we might go for a different solution. See bug 541588 for discussion.
Following up to the discussion in gentoo-dev, please add this line to the ebuild: RESTRICT="firebird? ( bindist )" and remove the bindist flag from IUSE and REQUIRED_USE.
Fixed.