title: sh: SET: command not found in `npm start`
body: <p>I'm trying to run a react project . and after I run command : npm start , it gave me an error:</p>
  
  <pre><code>sh: SET: command not found
  npm ERR! file sh
  npm ERR! code ELIFECYCLE
  npm ERR! errno ENOENT
  npm ERR! syscall spawn
  npm ERR! materials-trace@0.1.0 start: `SET PORT=3100 &amp;&amp; node scripts/start.js`
  npm ERR! spawn ENOENT
  npm ERR! 
  npm ERR! Failed at the materials-trace@0.1.0 start script.
  npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
  
  npm ERR! A complete log of this run can be found in:
  npm ERR!     /Users/jzhu321/.npm/_logs/2019-04-22T09_29_51_770Z-debug.log
  </code></pre>
  
  <p>and I have found the config here in <code>package.json</code> :</p>
  
  <pre><code>  "scripts": {
      "start": "SET PORT=3100 &amp;&amp; node scripts/start.js",
      "build": "node scripts/build.js",
      "test": "node scripts/test.js"
    },
  </code></pre>
  
  <p>How do I fix this problem?</p>