Parse build output into a rich format we can display properly

Created by: gaearon

The build overlay still looks less rich than the runtime one:

It would be nice to actually parse this (if it matches known Babel and ESLint formats) and display a richer version with:

• Error message and file information in a runtime stack frame-like view
• Highlighted line that causes the issue

There would need to be tests verifying we don't regress if message format updates.