If an encoding is specified, overwrite grunt.file.defaultEncoding.

```javascript
/*global module:false*/
module.exports = function (grunt) {
    grunt.file.defaultEncoding = 'gbk';
    grunt.initConfig({
        concat: {
            'all': {
                options: {
                    encoding: 'utf-8'
                },
                files: [
                    {
                        src: [
                            'resource/js/jquery-ui-1.9.2.custom.js',
                            'resource/js/jquery.cookie.js',
                            'resource/js/jquery.clickoutside.js',
                            'resource/js/jquery.bgiframe.js'
                        ],
                        dest: '../build/resource/js/main.js'
                    }
                ]
            }
        }
    });
};
```