can't build integ tests on mac osx

[navyxliu]

on mac osx, I can't link the 4 integ tests without hacking. I think we need to link some individual objects in opt.

I made a patch here. does it look reasonable? https://github.com/navyxliu/redex/commit/0a253564d849cceb7fbdd53a6cbe0f06097bebe2