New review comment by ahesford on void-packages repository

https://github.com/void-linux/void-packages/pull/24723#discussion_r487410310

Comment:
If you define your own `do_build` amd `do_install`, there is no value in using `build_style`, especially since the `haskell-stack` style pulls in the system GHC that you don't use. Just drop this line.