chore(CI): add if condition to check release published

Author: kkweon

.github/workflows/backend-build.yaml

@@ -50,9 +50,13 @@ jobs:
 
     needs:
       - release
+
+    if: ${{ needs.release.outputs.new_release_published }}
+
     steps:
       - uses: actions/checkout@v2
       - name: Docker meta
+        if: ${{ needs.release.outputs.new_release_published }}
         id: docker_meta
         uses: docker/metadata-action@v3
         with:
@@ -79,6 +83,7 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Build and push
+        if: ${{ needs.release.outputs.new_release_published }}
         uses: docker/build-push-action@v2
         with:
           context: ./server