Fix workflow: use direct docker commands instead of non-existent actions

.gitea/workflows/build.yml

@@ -7,20 +7,16 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
+    container:
+      image: catthehacker/ubuntu:act-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v3
 
       - name: Login to Gitea Registry
-        uses: actions/docker/login@v2
-        with:
-          registry: gitea.lokcal.de
-          username: loki
-          password: ${{ secrets.REGISTRY_PASSWORD }}
+        run: echo "${{ secrets.REGISTRY_PASSWORD }}" | docker login gitea.lokcal.de -u loki --password-stdin
 
       - name: Build and Push
-        uses: actions/docker/build-push@v4
-        with:
-          context: .
-          push: true
-          tags: gitea.lokcal.de/loki/arch-runner-custom-image:latest
+        run: |
+          docker build -t gitea.lokcal.de/loki/arch-runner-custom-image:latest .
+          docker push gitea.lokcal.de/loki/arch-runner-custom-image:latest