add github action to generate docker image for builder

.github/workflows/docker-image.yml

@@ -0,0 +1,50 @@
+name: Build and publish docker image
+
+on:
+  push:
+    # Publish `master` as Docker `latest` image.
+    branches:
+      - master
+      - develop
+
+    # Publish `v1.2.3` tags as releases.
+    tags:
+      - '*'
+env:
+  IMAGE_NAME: openwrt-builder
+
+jobs:
+  # Push image to GitHub Packages.
+  # See also https://docs.docker.com/docker-hub/builds/
+  push:
+    runs-on: ubuntu-latest
+    permissions:
+      packages: write
+      contents: read
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Build image
+        run: docker build . --file Dockerfile --tag $IMAGE_NAME --label "runnumber=${GITHUB_RUN_ID}"
+
+      - name: Log in to registry
+        # This is where you will update the PAT to GITHUB_TOKEN
+        run: echo "${{ secrets.GITHUB_TOKEN }}" | docker login ghcr.io -u $ --password-stdin
+
+      - name: Push image
+        run: |
+          IMAGE_ID=ghcr.io/${{ github.repository_owner }}/$IMAGE_NAME
+
+          # Change all uppercase to lowercase
+          IMAGE_ID=$(echo $IMAGE_ID | tr '[A-Z]' '[a-z]')
+          # Strip git ref prefix from version
+          VERSION=$(echo "${{ github.ref }}" | sed -e 's,.*/\(.*\),\1,')
+          # Strip "v" prefix from tag name
+          [[ "${{ github.ref }}" == "refs/tags/"* ]] && VERSION=$(echo $VERSION | sed -e 's/^v//')
+          # Use Docker `latest` tag convention
+          [ "$VERSION" == "master" ] && VERSION=latest
+          echo IMAGE_ID=$IMAGE_ID
+          echo VERSION=$VERSION
+          docker tag $IMAGE_NAME $IMAGE_ID:$VERSION
+          docker push $IMAGE_ID:$VERSION

Dockerfile

@@ -7,6 +7,8 @@ RUN apt-get update &&\
         flex gettext wget unzip xz-utils python python-distutils-extra \
         python3 python3-distutils-extra rsync curl libsnmp-dev liblzma-dev \
         libpam0g-dev cpio rsync && \
+    wget https://github.com/cli/cli/releases/download/v2.39.2/gh_2.39.2_linux_amd64.deb && \
+    apt-get install -f ./gh_2.39.2_linux_amd64.deb && \
     apt-get clean && \
     useradd -m user && \
     echo 'user ALL=NOPASSWD: ALL' > /etc/sudoers.d/user