Install this version:
emerge -a =games-emulation/stonesoup-libretro-9999-r1
If this version is masked, you can unmask it using the autounmask tool or standard emerge options:
autounmask =games-emulation/stonesoup-libretro-9999-r1
Or alternatively:
emerge --autounmask-write -a =games-emulation/stonesoup-libretro-9999-r1
# Copyright 2021 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2
EAPI=7
LIBRETRO_REPO_NAME="meancoot/stonesoup-libretro"
inherit git-r3 libretro-core
DESCRIPTION="Kibretro port of Dungeon Crawl - Stone Soup"
HOMEPAGE="https://github.com/meancoot/stonesoup-libretro"
KEYWORDS="~amd64 ~x86"
LICENSE="GPL-3"
SLOT="0"
DEPEND="dev-lang/lua:*"
RDEPEND="${DEPEND}
games-emulation/libretro-info"
S=${WORKDIR}/${PN}-${LIBRETRO_COMMIT_SHA}/crawl-ref
dev-lang/lua:*
dev-lang/lua:* games-emulation/libretro-info