Adds integration test for #3396

[denibertovic]

The provided test package (dinamo), that is part of a custom snapshot has
a malformed cabal file. Specifically, it's setting the required cabal
version to an invalid number (9001). This test makes sure that
stack does not care about this if we do not actually use the package
in our project.

Closes #3396

[denibertovic]

cc @snoyberg

[denibertovic]

Bah, let me know if I should get rid of the style changes in IntegrationSpec.hs (those were automatic). The only change there is just uncommenting "*.gz" in the toCopyRoot function... I'm not sure why it was commented out in the first place.

[snoyberg]

1. Please do roll back those style changes
2. I'm pretty sure the base-4.10.0.0.tar.gz file isn't necessary.
3. I think the Main.hs file needs to copy the custom.index.tar.gz file to $HOME/.stack/indices/CustomIndex/00-index.tar.gz before running stack build

[denibertovic]

@snoyberg I've added the necessary steps and removed the files we don't need, as well as the formatting.

One note though: We don't really need the invalid dinamo tarball nor do we need the custom.index.tar.gz file anymore but I thought it would be useful to keep them around if we ever needed to re-use in similar tests (so we don't have to create them from scratch again). What do you think?

[snoyberg]

Better not to copy over the cache, especially since the format will change over time. Also, I'd be interested in whether this works without the 00-index.tar file as well.

[denibertovic]

@snoyberg good point. Removing the cache file. Also, 00-index.tar is not needed so removing that as well.

[snoyberg]

I'd probably leave off the unnecessary tarballs for now, it shouldn't be too hard to recreate something similar.

[denibertovic]

@snoyberg Updated (removed tarballs that we don't need right now).