code: private boolean isClang() {
      final String command = getCommand();
      if (command == null) {
        return false;
      }
      if (command.startsWith("clang")) {
        return true;
      }
      if (!GPP_COMMAND.equals(command)) {
        return false;
      }
      final String[] cmd = {
          command, "--version"
      };
      final String[] cmdout = CaptureStreamHandler.execute(cmd).getStdout();
      return cmdout != null && cmdout.length > 0 && cmdout[0].contains("(clang-");
    }
docs: Checks whether the compiler is actually clang masquerading as gcc
  (e.g., the situation on OS X 10.9 Mavericks).