Include docker configs to build nixos images

vendor/docker-nixos/Dockerfile

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+FROM nixos/nix:2.24.11
+
+# Enable flakes
+RUN echo -e "experimental-features = nix-command flakes\n\
+builders-use-substitutes = true\n" >> /etc/nix/nix.conf
+# Enable remote builders substitutes
+# https://nix.dev/manual/nix/2.18/command-ref/conf-file.html?highlight=builders-use-substitutes#conf-builders-use-substitutes
+RUN echo "builders-use-substitutes = true" >> /etc/nix/nix.conf
+# Trust all directory to run flake commands as root on different volumes
+RUN git config --global --add safe.directory '*'
+
+# Copy the setup script
+COPY --chown=root:root --chmod=700 ./setup-remote.sh /setup-remote.sh

vendor/docker-nixos/README.txt

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+Slightly modified from [joshuachp/containers](https://github.com/joshuachp/containers/tree/e55ba5e5b8a3a39438e34f18459e358210742724/nixos).

vendor/docker-nixos/build.sh

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+#!/usr/bin/env bash
+
+set -exEuo pipefail
+
+git fetch --tags
+
+nixos_tag="$(
+    git tag |
+        grep '^nixos-' |
+        sed -e 's/^nixos-//' |
+        sort -V |
+        tail -n1
+)"
+
+if [ -z "$NIXOS_TAG" ]; then 
+  echo "Error: NIXOS_TAG is not set or is empty."
+  exit 1
+fi
+
+docker build \
+    --platform=linux/amd64,linux/arm64 \
+    -t "git.devcomp.xyz/devcomp/nixos:$NIXOS_TAG" \
+    -f Dockerfile \
+    --push .

vendor/docker-nixos/setup-remote.sh

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+#!/usr/bin/env bash
+
+set -exEuo pipefail
+
+mkdir -p ~/.ssh
+echo "$BUILDER_KEY" >>~/.ssh/id_ed25519
+echo "$BUILDER_HOST_KEYS" >>~/.ssh/known_hosts
+chmod -R 600 ~/.ssh
+
+# Check the remote builder
+nix store info --store "$BUILDERS"
+
+echo "$BUILDERS" >>/etc/nix/machines