Make stack warning about missing other-modules into an error (with flags)

[ndmitchell]

If I run stack build it says:

Warning: modules not listed in shake.cabal for 'shake' component (add to other-modules):
    Development.Ninja.Env

How can I turn that into an error so I can test for it in my continuous integration? stack build --Werror? Add a separate stack check target?

[mgsloan]

One option would be to extend the meaning of --pedantic to also turn warnings like this into errors (only for things that are always resolvable).

[ndmitchell]

I am happy to run with --Werror but my code is not --Wall clean, and I consider several of the Wall warnings to be actively harmful to code. Perhaps Stack should support both flags separately, as well as together with pedantic, then just Werror would have this effect.

[rvion]

I love this new flag idea, and also agree that not all Wall warnings should become errors with this flag

[borsboom]

If anyone wants to work on a PR, that would be welcome.

[TheWizardTower]

This looks like a fun nugget to chew on. I'll tackle this. :)