ci: use custom container

.forgejo/workflows/build.yml

@@ -6,6 +6,10 @@ on:
 
 jobs:
   docker:
+    container:
+      image: docker:24.0-dind
+      options: --privileged
+
     permissions:
       contents: read
       packages: write
@@ -14,10 +18,8 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Set up Docker
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y docker.io
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
 
       - name: Log in to GitHub Container Registry
         uses: docker/login-action@v3