The current dev-util/build-0.3.9 ebuild works for 0.3.10 without modifications. Could you please give it a bump?
commit 3fe0b5b4748d1d23bb49b1ac46d5fffdeaa4cc2b Author: David Seifert <soap@gentoo.org> Date: Sat Oct 15 14:51:24 2016 +0200 dev-util/build: Version bump to 0.3.10 Gentoo-bug: 585736 * EAPI=6