title: env step parameter in cloudbuild.yaml file not settings environment variable
body: <p>My <code>cloudbuild.yaml</code> file looks like</p>
  
  <pre><code>steps:
    # build the container image
    - name: "gcr.io/cloud-builders/docker"
      args: ["build", "-t", "gcr.io/$PROJECT_ID/backend:$COMMIT_SHA", "."]
      env:
        - "APP_ENV=production"
    # push the container image to Container Registry
    - name: "gcr.io/cloud-builders/docker"
      args: ["push", "gcr.io/$PROJECT_ID/backend:$COMMIT_SHA"]
    # Deploy container image to Cloud Run
    - name: "gcr.io/cloud-builders/gcloud"
      args:
        - "run"
        - "deploy"
        - "backend"
        - "--image"
        - "gcr.io/$PROJECT_ID/backend:$COMMIT_SHA"
        - "--region"
        - "us-central1"
        - "--platform"
        - "managed"
  images:
    - "gcr.io/$PROJECT_ID/backend:$COMMIT_SHA"
  
  </code></pre>
  
  <p>and it builds and deploys a new container to Cloud Run, however it doesn't set the APP_ENV environment variable to <code>"production"</code>. Why is that and how do I get it to?</p>
  
  <p>I am following <a href="https://cloud.google.com/cloud-build/docs/build-config" rel="nofollow noreferrer">this guide</a>.</p>