add CI files

.docker/Dockerfile

@@ -0,0 +1,26 @@
+FROM gentoo/stage3:latest
+
+COPY ./. /
+
+RUN getuto
+
+RUN emerge-webrsync
+
+RUN emerge \
+    =dev-lang/rust-bin-9999 \
+    llvm-core/clang \
+    llvm-core/lld \
+    dev-vcs/git \
+    sys-process/parallel
+
+RUN git clone https://jturnerusa.dev/cgit/ebuilds/ /var/db/repos/spawns
+
+COPY etc/portage/repos.conf /etc/portage/
+
+RUN mkdir -p /var/cache/distfiles/git3-src && chown portage:portage /var/cache/distfiles/git3-src
+
+RUN emerge =dev-build/meson-9999
+
+WORKDIR /workspace
+
+ENTRYPOINT /bin/bash

.docker/etc/portage/make.conf

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+BINPKG_FORMAT="gpkg"
+FEATURES="binpkg-request-signature getbinpkg -ipc-sandbox -network-sandbox -pid-sandbox -userfetch -news"

.docker/etc/portage/package.accept_keywords/meson

@@ -0,0 +1 @@
+dev-build/meson **

.docker/etc/portage/package.accept_keywords/rust-bin

@@ -0,0 +1 @@
+dev-lang/rust-bin **

.docker/etc/portage/package.use/rust-bin

@@ -0,0 +1 @@
+dev-lang/rust-bin clippy rustfmt 

.docker/etc/portage/repos.conf

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+[DEFAULT]
+main-repo = gentoo
+
+[gentoo]
+location = /var/db/repos/gentoo
+sync-type = rsync
+sync-uri = rsync://rsync.gentoo.org/gentoo-portage
+auto-sync = yes
+sync-rsync-verify-jobs = 1
+sync-rsync-verify-metamanifest = yes
+sync-rsync-verify-max-age = 3
+sync-openpgp-key-path = /usr/share/openpgp-keys/gentoo-release.asc
+sync-openpgp-keyserver = hkps://keys.gentoo.org
+sync-openpgp-key-refresh-retry-count = 40
+sync-openpgp-key-refresh-retry-overall-timeout = 1200
+sync-openpgp-key-refresh-retry-delay-exp-base = 2
+sync-openpgp-key-refresh-retry-delay-max = 60
+sync-openpgp-key-refresh-retry-delay-mult = 4
+sync-webrsync-verify-signature = yes
+sync-git-verify-commit-signature = true
+
+[spawns]
+location = /var/db/repos/spawns
+sync-uri = https://jturnerusa.dev/cgit/ebuilds