Prevent skip in docker-compose
<p>I have a <code>docker-compose.yml</code> for a Django web app with a backend. It looks like this:</p>

<pre><code>version: '2'

services:
  db:
    image: # special image
    ports:
      - "1433:1433"
    environment:
      PASSWORD: "*********"

  web:
    build: .
    command: python manage.py runserver 0.0.0.0:8000
    ports:
      - "8000:8000"
    depends_on:
      - db
</code></pre>

<p>When I run <code>sudo docker-compose build</code>, the first line of output says </p>

<pre><code>db uses an image, skipping. 
Building web.
</code></pre>

<p>I need the <code>db</code> image to be built before <code>web</code>. </p>

<p>How can I make the <code>db</code> image get built first?</p>