Add bail option to production webpack config

[duebbert]

webpack happily ignores build errors which is ok for development but when creating production files it should fail.

The configuration option bail should be used for this and results in a build to throw an error when a problem is encountered instead of continuing.

Proposal: add bail: true to the configuration in build/webpack.prod.conf.js

[LinusBorg]

I think this makes sense. Sorry for overlooking it for so long.