title: webpack - turn off watch from commandline
body: <p>I have a webpack config that is setup to watch for changes. </p>
  
  <p>Once in a while, I would like to just run the build one time and then exit. </p>
  
  <p>I solve this now by typing <code>npm run dev</code> (which runs <code>webpack --config &lt;config.json&gt;</code>), and then hit <code>Ctrl+C</code> when it's done with the first build cycle. </p>
  
  <p>Is there a command line switch that I can use to overrule the watch setting from the config? Something like an negated <code>--watch</code> switch? A <code>--do-not-watch</code> option?</p>