[WIP] Add gentoo-base.

gentoo-base.Dockerfile

@@ -0,0 +1,31 @@
+# Portage tree.
+FROM gentoo/portage:latest as portage
+
+# Build packages in /workdir.
+FROM gentoo/stage3-amd64:latest as build
+COPY --from=portage /var/db/repos/gentoo /var/db/repos/gentoo
+RUN sed -i 's/-O2/-Os/' /etc/portage/make.conf
+RUN echo -e '\n# Added by tastytea/gentoo-base:' >> /etc/portage/make.conf
+# Bug 680456.
+RUN echo 'FEATURES="-ipc-sandbox -mount-sandbox -network-sandbox -pid-sandbox \
+    -sandbox -usersandbox"' >> /etc/portage/make.conf
+RUN echo 'MAKEOPTS="-j1"' >> /etc/portage/make.conf
+RUN echo 'USE="minimal -cracklib -gpg -ncurses -nls -pam -pcre -pcre-jit -perl \
+    -readline -rsync-verify"' >> /etc/portage/make.conf
+RUN eselect profile set default/linux/amd64/17.1
+RUN quickpkg --include-config=y @system sys-libs/glibc \
+    app-portage/elt-patches dev-lang/perl
+RUN emerge --root=/workdir --usepkgonly --nodeps --quiet \
+    app-portage/elt-patches dev-lang/perl
+RUN emerge --root=/workdir --root-deps --usepkg --quiet sys-apps/portage
+RUN cp /etc/portage/make.conf /workdir/etc/portage/make.conf
+RUN rm -r /workdir/usr/share/{doc,i18n,locale,man,zoneinfo}
+
+# Final image.
+FROM scratch
+LABEL maintainer="tastytea+docker@tastytea.de"
+LABEL description="[WIP] My base for Gentoo images."
+COPY --from=build /workdir /
+
+# TODO: Mount distfiles.
+# TODO: Use ccache with data on external volume.