Fix clang build breakage (-Werror -Wformat).

      //

      // TODO(narayan): This will be an error in a future android release.

      // error = true;

      ALOGW("Zygote opened %d new file descriptor(s).", open_fds.size());

      ALOGW("Zygote opened %zd new file descriptor(s).", open_fds.size());

      // TODO(narayan): This code will be removed in a future android release.

      std::set<int>::const_iterator it;