Create branch for Haskell build changes and updates?

[John Kehayias]

Hello,

There have been several recent bug reports and patches (list below) that could 
be addressed with some changes to haskell-build-system, the Hackage importer, 
and some package updates. Given the number of packages affected, it was 
discussed on #guix that it would be good to have a branch for these changes and 
to have Cuirass build the Haskell packages to look for breakage.

How do we feel about this? I'm happy to help with some patches I've submitted 
and update some packages, though it would also be good to have someone 
experienced with Haskell packaging and/or Guix too. (I'm new to both, but I've 
had success with my patches at least, locally.)

Here is a (partial) list of the most recent bugs and patches that would belong 
on this branch:

- https://issues.guix.gnu.org/48944 (build failure for new package, addressed 
by next patch)

- https://issues.guix.gnu.org/49199 (patch to add package-db to runhaskell to 
help with non-trivial configure stage; worked around in existing packages with 
a TODO marked to make this change actually)

- https://issues.guix.gnu.org/49418 (metadata revisions not imported, so e.g. 
dependency requirements out of date)

- https://issues.guix.gnu.org/49326 (bug with specifying ghc version for 
building)

- https://issues.guix.gnu.org/49320 (importer doesn't support some stages)

- https://issues.guix.gnu.org/48999 (local source for Haskell packages)

I'm not sure what we would want to include or not in such a branch, but I think 
it would make sense to put together the build-system and related changes at 
least. Some package updates (like a ghc version) would also affect a lot of 
packages, so might be good to do that together as well.

Thanks,
John