Please check whether the use of 'einstall' in this ebuild is actually needed. From a quick glance at the Makefile, it seems to have proper support for DESTDIR. Therefore, if possible please replace the call to 'einstall' with proper 'default' or 'emake DESTDIR="${D}" install'. Thanks.
Fixed simultaneously with bug 527048 commit 424b27deb88c082388f24b6f0be39e8adfc1fa17 Author: David Seifert <soap@gentoo.org> Date: Tue Jan 12 19:44:32 2016 +0100 media-sound/tap-reverbed: Revbump and overhaul ebuild to EAPI=6, #527048