title: Babel seems to ignore NODE_ENV
body: <p>According to the docs Babel will use NODE_ENV to set env specific options if BABEL_ENV is not specified. I noticed today that this doesn't work, or at least on my machine.</p>
  
  <p><strong>package.json</strong></p>
  
  <pre><code>{
    "name": "babel-exp",
    "version": "1.0.0",
    "main": "index.js",
    "license": "MIT",
    "scripts": {
      "start1": "NODE_ENV=foo babel-node src/index",
      "start2": "BABEL_ENV=foo babel-node src/index"
    },
    "dependencies": {
      "babel-cli": "^6.24.1",
      "babel-preset-env": "^1.5.1"
    }
  }
  </code></pre>
  
  <p><strong>.babelrc</strong></p>
  
  <pre><code>{
    "env": {
      "foo": {
        "presets": ["env"]
      }
    }
  }
  </code></pre>
  
  <p><strong>src/index.js</strong></p>
  
  <pre><code>import { hello, bye } from './sayings'
  
  console.log('hello = ', hello);
  </code></pre>
  
  <p><strong>src/sayings.js</strong></p>
  
  <pre><code>export const hello = 'hello'
  export const bye = 'bye'
  </code></pre>
  
  <p>Running start1 with either npm or yarn results in: <code>SyntaxError: Unexpected token import</code>
  start2 logs <code>hello =  hello</code> correctly</p>
  
  <p>node: v7.10.0
  yarn: v0.24.6
  npm: 4.1.1</p>
  
  <p>I suppose the folks at Babel didn't change this behaviour, so it's probably something I am doing wrong. I would be happy if someone can verify this problem, or provide any other feedback.</p>