Support of "doBenchmark" parameter

[qrilka]

It doesn't appear as a field in Derivation and also there's no option about it in CLI flags. Is it OK to add in in a PR or maybe there's some reason behind not having it?

[basvandijk]

Note that we already have a doBenchmark function in nixpkgs. Why do we need it as a parameter of Derivation?

[qrilka]

@basvandijk cabal2nix already exposes doCheck and runHaddock (BTW I don't quite understand why is it not doHaddock) and flags --no-haddock and --no-check to set them in the produced derivation. My idea is to have an uniform API and expose doBenchmark in cabal2nix as well.
Alternatively we could get the same result (uniform API) with functions from pkgs.haskell.lib but that will be a breaking change in cabal2nix and also it introduces some overhead of calling those functions.
I think the former would give a bit better API for cabal2nix users.

[peti]

I believe that doBenchmark is absent simply because nobody had asked for it yet. Personally, I wouldn't mind merging a PR that adds support for this particular feature. If it's useful to you, then feel free to go ahead and add it.