That’s a pretty old commit (from April 4th) and you were so unlucky to actually find yourself in one of the very rare commits in master that happen to be broken.
If you want to compile ROOT master, pull a more recent version with git pull. Otherwise, I would suggest you check out one of the patch releases, which are not in active development and are more stable, e.g. git checkout v6-20-00-patches.
I am not a mac user, but I hear good things about brew install root, i.e. a ROOT installation via homebrew (see here).
Cheers,
Enrico