Extract IS_EE config helper

(cherry picked from commit baa671a3)

config/helpers/is_ee_env.js

+const fs = require('fs');
+const path = require('path');
+
+const ROOT_PATH = path.resolve(__dirname, '../..');
+
+module.exports =
+  process.env.EE !== undefined
+    ? JSON.parse(process.env.EE)
+    : fs.existsSync(path.join(ROOT_PATH, 'ee'));

config/webpack.config.js

-const fs = require('fs');
 const path = require('path');
 const glob = require('glob');
 const webpack = require('webpack');
@@ -12,10 +11,7 @@ const ROOT_PATH = path.resolve(__dirname, '..');
 const CACHE_PATH = process.env.WEBPACK_CACHE_PATH || path.join(ROOT_PATH, 'tmp/cache');
 const IS_PRODUCTION = process.env.NODE_ENV === 'production';
 const IS_DEV_SERVER = process.argv.join(' ').indexOf('webpack-dev-server') !== -1;
-const IS_EE =
-  process.env.EE !== undefined
-    ? JSON.parse(process.env.EE)
-    : fs.existsSync(path.join(ROOT_PATH, 'ee'));
+const IS_EE = require('./helpers/is_ee_env');
 const DEV_SERVER_HOST = process.env.DEV_SERVER_HOST || 'localhost';
 const DEV_SERVER_PORT = parseInt(process.env.DEV_SERVER_PORT, 10) || 3808;
 const DEV_SERVER_LIVERELOAD = IS_DEV_SERVER && process.env.DEV_SERVER_LIVERELOAD !== 'false';