build: use needs-updating condition

.gitea/workflows/nightly.yaml

@@ -28,17 +28,17 @@ jobs:
         with:
           base-image: roundcube/roundcubemail:latest-apache
           image: zeguigui/roundcubemail:latest-apache 
-      - name: Needs updating
-        run: echo "Needs updating ${{ steps.checkupdate.outputs.needs-updating }}"
       - name: Set up docker buildx
         uses: docker/setup-buildx-action@v3
         with:
           driver-opts: |
             network=giteanet
+        if: steps.checkupdate.outputs.needs-updating == 'true'
       - name: Build and push version
         uses: docker/build-push-action@v5
         env:
           ACTIONS_RUNTIME_TOKEN: ''
         with:
           push: true
-          tags: zeguigui/roundcubemail:latest-apache
+          tags: zeguigui/roundcubemail:latest-apache
+        if: steps.checkupdate.outputs.needs-updating == 'true'