Hi,
Please read the README linked in the previous email. It provides all the information you've asked about, including step-by-step instructions for building. If you have specific questions after reading that document, I would be happy to answer them.
You have the option of using whichever compiler you'd like. We officially only support an Xcode+clang toolchain on macOS, so if you are unfamiliar with building a C++ application it would be best to use that, because you will be able to follow the instructions without modification. gcc should work, as should a distribution of clang not bundled with Xcode. As far as I know, you can get both through homebrew.
-Brian