Can I output only a css file using an entry point?

Question

I'm trying to find a way to only output a .css file and not a .js file with it. I cannot seem to find an automated way to handle this.

Example (simplified)

entry: {
    polyfill: [
        'babel-polyfill',
        'react-fastclick'
    ],

    app: [
        './js/index.js',
    ],

    styles: [
        './styles/global.scss'
    ]
}

Because I want to use [chunkname] for caching purposes, I cannot append the global.scss to the app entry.

Any ideas on how to not output a .js file for the styles entry?