As discussed in gentoo-dev, live ebuilds must not have any KEYWORDS: https://archives.gentoo.org/gentoo-dev/message/a4cc194fc387d4abffed054b523d83f8 Policy reference: "VCS ebuilds must be with empty KEYWORDS but not package.masked (except if the mask is for an independent reason). Usually the KEYWORDS line should be omitted altogether. This applies to "live" ebuilds (-9999) and to ebuilds that extract a static revision but still use a version control system for fetching." https://devmanual.gentoo.org/ebuild-writing/functions/src_unpack/vcs-sources/index.html
It may be preferable to fetch the snapshot provided by github instead, i.e.: https://github.com/OGRECave/ogre-next/archive/${COMMIT}.tar.gz
Can be fixed with https://github.com/gentoo/gentoo/pull/15527 (Ogre-2.1 first major release)
