How to change compiler in Xcode C++

Question

I've been searching for quite some time, and I can't seem to find out how to change the compiler on the latest Xcode. I am not sure what it is set at currently, but I'd like to change it to GCC if possible. Right now my homework example will not recognize ptrace.h, so I think it might have to do with the chosen compiler.

Answer 1

Screenshot of Build Rules:

You can add a rule for C++, click the "+" to the right of "Custom".

Answer 2

Select the project in the browser, then navigate to...