Building assignment 2 on Mac OS is a little bit more involved than the previous two assignments. You'll need to install a copy of FLTK. I suggest using Homebrew for this. Once you've got homebrew installed, just run:
brew install fltk
Another thing: since we've been relying so heavily on vecmath for all of the projects, I went ahead and made a separate repository for it. To grab vecmath, just call:
git submodule init && git submodule update
Now, you should be able to call make as usual.
Enjoy. Email me if you run into any issues.