Url rewriting not working outside Laravel for Mix

I am using following config in my webpack.mix.js file

mix.options({
    publicPath: 'assets'
});
mix.styles([
        'assets/v3/plugins/pace/pace-theme-flash.css',
        'assets/v3/plugins/boostrapv3/css/bootstrap.min.css',
        'assets/v3/plugins/font-awesome/css/font-awesome.css',
        'assets/v3/plugins/jquery-scrollbar/jquery.scrollbar.css',
        'assets/v3/framework/css/pages-icons.min.css',
        'assets/v3/framework/css/pages.min.css',
        'assets/v3/framework/css/themes/corporate.min.css',
        'assets/v3/css/style.css'
    ], 'assets/compiled/css/core.css');

But the image/font urls in the files are not rewritten in the final combined file. I am using this outside laravel.

I am using laravel-mix version 2.1.14.