Add zmk builder image (#12)

Reviewed-on: #12
Co-authored-by: Jan Klattenhoff <jan@kjan.de>
Co-committed-by: Jan Klattenhoff <jan@kjan.de>

.gitea/workflows/zmk-builder.yaml

@@ -0,0 +1,64 @@
+name: ZMK builder
+on:
+  schedule:
+    - cron: "@weekly"
+  push:
+    branches: [main]
+    paths:
+      - .gitea/workflows/zmk-builder.yaml
+      - images/actions/zmk-builder/**
+  pull_request:
+    
+jobs:
+  build:
+    name: Build and push image
+    runs-on: ubuntu-latest
+    container: catthehacker/ubuntu:act-latest
+
+    steps:
+    - name: Checkout
+      uses: https://git.kjan.de/actions/checkout@v4
+
+    - name: Set up Docker Buildx
+      uses: https://git.kjan.de/actions/setup-buildx-action@v3
+
+    - name: Login to local Docker Registry
+      uses: https://git.kjan.de/actions/login-action@v3
+      with:
+        registry: git.kjan.de
+        username: ${{ secrets.REGISTRY_USERNAME }}
+        password: ${{ secrets.REGISTRY_TOKEN }}
+
+    - name: Login to Docker.io Registry
+      uses: https://git.kjan.de/actions/login-action@v3
+      with:
+        username: ${{ secrets.DOCKER_USERNAME }}
+        password: ${{ secrets.DOCKER_PASSWORD }}
+
+    - name: Cache Docker layers
+      uses: actions/cache@v4
+      with:
+        path: /tmp/.buildx-cache
+        key: ${{ runner.os }}-zmk-builder-${{ github.sha }}
+        restore-keys: |
+          ${{ runner.os }}-zmk-builder-                
+
+    - name: Build and push
+      uses: https://git.kjan.de/actions/build-push-action@v6
+      with:
+        cache-from: type=local,src=/tmp/.buildx-cache
+        cache-to: type=local,dest=/tmp/.buildx-cache-new,mode=max
+        context: ./images/actions/zmk-builder
+        push: ${{ github.ref == 'refs/heads/main' }}
+        tags: |
+          git.kjan.de/actions/zmk-builder:latest
+          git.kjan.de/actions/zmk-builder:${{ gitea.sha }}             
+
+    - # Temp fix
+      # https://github.com/docker/build-push-action/issues/252
+      # https://github.com/moby/buildkit/issues/1896
+      name: Move cache
+      run: |
+        rm -rf /tmp/.buildx-cache
+        mv /tmp/.buildx-cache-new /tmp/.buildx-cache                       
+

images/actions/zmk-builder/Dockerfile

@@ -0,0 +1,4 @@
+FROM zmkfirmware/zmk-build-arm:stable
+
+RUN apt-get update
+RUN apt-get install --yes --no-install-recommends nodejs zstd zip