infra: add dockerfile used for gentoo-utils

.docker/Dockerfile

@@ -0,0 +1,35 @@
+FROM gentoo/stage3:latest
+
+USER root
+
+# Fix permissions for distfiles directory
+RUN mkdir -p /var/cache/distfiles && \
+    chmod 755 /var/cache/distfiles && \
+    chown -R portage:portage /var/cache/distfiles
+
+# enable bintoo
+RUN echo "BINPKG_FORMAT=\"gpkg\"" >> /etc/portage/make.conf
+RUN echo "EMERGE_DEFAULT_OPTS=\"\${EMERGE_DEFAULT_OPTS} --getbinpkg\"" >> /etc/portage/make.conf
+RUN echo "FEATURES=\"getbinpkg\"" >> /etc/portage/make.conf
+
+RUN getuto
+
+RUN emerge-webrsync && \
+    emerge --sync
+
+# get super latest meson
+RUN echo "=dev-build/meson-9999 **" >> /etc/portage/package.accept_keywords/package.accept
+RUN emerge --ask=n =dev-build/meson-9999
+RUN meson --version
+
+# install nightly rust
+RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain nightly
+RUN source "$HOME/.cargo/env" && rustc --version && cargo --version
+
+RUN emerge --ask=n dev-vcs/git
+
+# Set working directory
+WORKDIR /workspace
+
+# Default command
+CMD ["/bin/bash"]