feat(bundle): only use prod bundle for production build

[bigopon]

All the v2 packages are with 2 dist types:

• dev: bundled source, with error message and property names as is.
• prod: bundled source, with minified error message and mangled property names.

This PR adds a tweak to make the production flag control the switch between these 2 bundles, so that development experience will be better.