You can do this:
const someGcc = defined(gcc) or defined(llvm_gcc) or defined(clang) Run
const someGcc = defined(gcc) or defined(llvm_gcc) or defined(clang)
defined(cpp) C++ targetdefined(objc) Objective C targetdefined(js) JavaScript target
I don't think there is a define for the "C target", but you can use not defined(cpp) and not defined(objc) and not defined(js) for this.