sarga/packages/Webkul/Admin/webpack.mix.js

const { mix } = require('laravel-mix');
require('laravel-mix-merge-manifest');

// var publicPath = 'publishable/assets';
var publicPath = '../../../public/vendor/webkul/admin/assets';

mix.setPublicPath(publicPath).mergeManifest();

mix.js(__dirname + '/src/Resources/assets/js/app.js', 'js/admin.js')
    .copyDirectory( __dirname + '/src/Resources/assets/images', publicPath + '/images')
    .sass( __dirname + '/src/Resources/assets/sass/app.scss', 'css/admin.css')
    .options({
        'processCssUrls': false
    });

if (mix.inProduction()) {
    mix.version();
}