title: Why is Swift build command only available in development?
body: <p>I'm learning Swift now, and I found out that the <code>swift build</code> command is available only in the development version of Swift. </p>
  
  <p>So when I invoke </p>
  
  <pre><code>swift build 
  </code></pre>
  
  <p>...it returns: </p>
  
  <blockquote>
    <p>swift build unable to invoke subcommand. </p>
  </blockquote>
  
  <p>Can someone explain why? </p>
  
  <p>In <a href="https://stackoverflow.com/a/35010843/5612645">another answer</a> I found the above command, but why is it only available in the development version?</p>