title: Dockerfile define multiple ARG arguments in a single line
body: <p>Right now I am defining <strong>ARG</strong>s in my Dockerfile like this:</p>
  
  <pre><code>ARG CDN_ENDPOINT
  ARG AWS_S3_BUCKET
  </code></pre>
  
  <p>Is there a way to define them in a single line similar to <strong>ENV</strong> to avoid creating extra layers in docker image like this:</p>
  
  <pre><code>ENV CDN_ENDPOINT=endpoint \
      AWS_S3_BUCKET=bucket
  </code></pre>