title: Pass env file to detox
body: <p>I would like to pass environment variable when I run detox tests in my react-native app: </p>
  
  <pre><code> "ios.sim.debug": {
      "binaryPath": "ios/build/Build/Products/Debug-iphonesimulator/myapp.app",
      "build": "export IS_DETOX=true &amp;&amp; xcodebuild -workspace ios/myapp.xcworkspace -scheme my app -configuration Debug -sdk iphonesimulator -derivedDataPath ios/build",
      "type": "ios.simulator",
      "device": {
        "type": "iPhone 11 Pro"
      }
    }
  </code></pre>
  
  <p>I've installed <a href="https://github.com/luggit/react-native-config" rel="nofollow noreferrer">react-native-config</a>. But the variable IS_DETOX is undefined in JS when I run detox tests.</p>
  
  <p>Thanks</p>