Install this version:
emerge -a =app-eselect/eselect-gradle-0.1
If this version is masked, you can unmask it using the autounmask tool or standard emerge options:
autounmask =app-eselect/eselect-gradle-0.1
Or alternatively:
emerge --autounmask-write -a =app-eselect/eselect-gradle-0.1
# Copyright 1999-2019 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2
EAPI=6
DESCRIPTION="Manage multiple Gradle versions on one system"
HOMEPAGE="https://www.gentoo.org"
SRC_URI=""
LICENSE="GPL-2"
SLOT="0"
KEYWORDS="~amd64 ~x86"
IUSE=""
DEPEND=""
RDEPEND="app-admin/eselect"
S="${WORKDIR}"
src_install() {
insinto /usr/share/eselect/modules
doins "${FILESDIR}/gradle.eselect"
}