Any ways to test a GHC build against large set of packages (including test suites)?

[Ömer Sinan Ağacan]

Hi,

I'd like to test some GHC builds + some compile and runtime flag combinations
against a large set of packages by building them and running test suites. For
this I need

- A set of packages that are known to work with latest GHC
- A way to build them and run their test suites (if I could specify compile and
  runtime flags that'd be even better)

I think stackage can serve as (1) but I don't know how to do (2). Can anyone
point me to the right direction? I vaguely remember some nix-based solution for
this that was being discussed on the IRC channel, but can't recall any details.

Thanks,

Ömer