Add back OSX build flags that were missed in CMake
Add back OSX build flags that were missed in CMake

ponylang/ponyc,jemc/ponyc,sgebbie/ponyc,ponylang/ponyc,dipinhora/ponyc,dipinhora/ponyc,jemc/ponyc,sgebbie/ponyc,ponylang/ponyc,dipinhora/ponyc,sgebbie/ponyc,sgebbie/ponyc,jemc/ponyc,sgebbie/ponyc