added external babel helpers plugin

scripts/rollup/build.js

@@ -120,7 +120,7 @@ function updateBabelConfig(babelOpts, bundleType) {
       newOpts = Object.assign({}, babelOpts);
 
       // for FB, we don't want the devExpressionWithCodes plugin to run
-      newOpts.plugins = [];
+      newOpts.plugins = [require.resolve('babel-plugin-external-helpers')];
       return newOpts;
   }
 }

scripts/rollup/bundles.js

@@ -24,6 +24,7 @@ const babelOptsReact = {
 const babelOptsReactART = Object.assign({}, babelOptsReact, {
   // Include JSX
   presets: [require.resolve('babel-preset-react')],
+  plugins: [require.resolve('babel-plugin-external-helpers')],
 });
 
 const bundles = [