Missing library in Mac OS X instructions?

Hi, I tried to get GHC working from the repo in Mac OS X following the instructions in https://gitlab.haskell.org/ghc/ghc/wikis/building/preparation/mac-osx. At first I got the "error __GNU_MP_VERSION not defined" problem, for which the guide recommends to prepend "CC=clang" to "./configure" , which I did. But even then, I also had to install "gmp" using "brew install gmp". 1. Is it right that I need to install gmp using brew or did I miss some previous step? 2. If (1) is affirmative, how can I help update the docs for building in Mac OS X? Regards, Alejandro