New review comment by waynevanson on void-packages repository

https://github.com/void-linux/void-packages/pull/24723#discussion_r487492802

Comment:
> > I think the problem here is that stack downloads a version of ghc
> 
> Isn't this a problem on its own?

Because ideally we want to use an xbps package, right? As I said in a comment, we need to download a specific, non-lts version  of GHC.