Output logging level for build

Created by: eddiemonge

By default (and I haven't found a way to change), the output from npm run build is very verbose and mostly unnecessary (after the first run). It would be nice if there was a way to specify log level to turn it off.

The logging is output here: https://github.com/facebook/create-react-app/blob/7b1a32be6ec9f99a6c9a3c66813f3ac09c4736b9/packages/react-scripts/scripts/build.js#L85-L123