code: def _host_libc(self):
      
      libc_dir_option = self.get_options().libc_dir
      if libc_dir_option:
        maybe_libc_crti = os.path.join(libc_dir_option, self._LIBC_INIT_OBJECT_FILE)
        if os.path.isfile(maybe_libc_crti):
          return HostLibcDev(crti_object=maybe_libc_crti,
                             fingerprint=hash_file(maybe_libc_crti))
        raise self.HostLibcDevResolutionError(
          "Could not locate {} in directory {} provided by the --libc-dir option."
          .format(self._LIBC_INIT_OBJECT_FILE, libc_dir_option))
  
      return self._get_host_libc_from_host_compiler()
docs: Use the --libc-dir option if provided, otherwise invoke a host compiler to find libc dev.