title: Docker GitHub actions with parameters on build step
body: <p>I am looking if it's possible to build a docker container from a Dockerfile with args.</p>
  
  <p>The purpose is to have a dynamic "FROM" in the Dockerfile.
  So in the <code>FROM circleci/android:api-28</code>, the <code>api-28</code> to be a parameter</p>
  
  <p>So for a constant given Dockerfile:</p>
  
  <pre><code>FROM circleci/android:api-28    
  COPY entrypoint.sh /entrypoint.sh    
  RUN sudo chmod +x entrypoint.sh    
  
  ENTRYPOINT [ "/entrypoint.sh" ]
  </code></pre>
  
  <p>Github actions build the following image:</p>
  
  <pre><code>Build Diolor/Android-build-action@master2m 8s
  Successfully tagged 2e4e3a:89928963f88542989ff9d771e524d2d6
  Build container for action use: '/home/runner/work/_actions/Diolor/Android-build-action/master/Dockerfile'.
  /usr/bin/docker build -t 2e4e3a:89928963f88542989ff9d771e524d2d6 "/home/runner/work/_actions/Diolor/Android-build-action/master"
  </code></pre>
  
  <p>Does Github Actions allow environment params or arg params on that build step?</p>
  
  <p>The goal is the Action consumer to use a different docker container tag, if he desires.</p>