Update GHC and package dependency version pinning

[atomb]

No description provided.

[RyanGlScott]

As far as why this is failing on Windows in particular, see http://hackage.haskell.org/package/hsc2hs-0.68.7/hsc2hs.cabal. To work around a Windows-specific process bug, that version of hsc2hsrequires process >= 1.6.8, which is more recent that what is pinned in the .config file.

One possible way to fix this would be to re-freeze the files but with hsc2hs==0.68.6, which doesn't have quite as restrictive version bounds on process for Windows.

[RyanGlScott]

This looks sensible, although I worry that we'll have similar difficulties later when we try to update the .config files. Can you document somewhere the series of additional steps you needed to apply on top of cabal freeze to make things work? Better yet would be scripting these additional scripts, but perhaps that's not feasible.

[atomb]

I ultimately want this to be completely automated, and think it could be, but it'll take more work, and until we do at least part of this commit we can't build using GHC 8.10.3, which it's important for us to be able to do.

What I'd like in the long run would be to have some sort of automated process that would try running cabal freeze on each platform, try to build, and create a PR if the build succeeds. That way we could keep building against the latest libraries, but only through an easy, opt-in process.

There were some manual changes needed here because of some reorganization we've been doing. After this merge, I think the only manual changes would be to remove platform-specific entries. Alternatively, we could have separate freeze files for Windows (which we've done in the past), which should eliminate any need to do manual work.

[RyanGlScott]

OK. I'm fine with merging this as-is, but I do think it's worth writing down what the platform-specific packages are somewhere, as that could save someone else some pain down the road.

[atomb]

Yes, that's a very good point. I just pushed a commit to the README outlining what packages to leave out of freeze files.

[RyanGlScott]

Looks good to me.

Now that we have Mergify enabled, I'm going to try to see if I can get this automatically merged once CI passes by applying the new "ready-to-merge" label.

[atomb]

Whee! That'll be awesome. :) I'm so happy to have Mergify.

[brianhuffman]

@atomb If you want to give your approval to #1059 then we can see have a race and see how mergify handles it

[brianhuffman]

@atomb: So #1059 got merged first, and now this one's out of date with master. I think we need a "keep-updated" label if we want Mergify to automatically rebase and restart the CI when that happens. (That label doesn't exist yet; we should double check to make sure we name it the right thing.)

Also, I see some CI failures with the message "Error: retrieving gpg key timed out" which probably have nothing to do with this PR.