postCssLoaderOptions(preprocessor) {
        return {
            sourceMap: this.context.isUsing('sourcemaps'),
            postcssOptions: {
                plugins: new PostCssPluginsFactory(this.context).load(
                    preprocessor.postCssPlugins
                ),
                hideNothingWarning: true
            }
        };
    }
Generate the options object for the PostCSS Loader.

@param {Detail} preprocessor