fix Flow failure breaking yarn run build

Summary:
`flow-api-translator` can't handle `module.exports`.  Shift this to ESM style exports like the other built packages.

Changelog: [Internal] - Fixing an internal build script broken by D56243647

Reviewed By: cipolleschi

Differential Revision: D56638506

fbshipit-source-id: f5a4c7bea06b7f95300388e3d37cf0d377bc3b17

packages/core-cli-utils/src/index.js

@@ -31,4 +31,4 @@ if (!process.env.BUILD_EXCLUDE_BABEL_REGISTER) {
   }
 }
 
-module.exports = require('./index.flow.js');
+export * from './index.flow.js';