message: Fix format string issue introduced in r340548
  Make format string portable.
diff: @@ -126,7 +126,7 @@ bool lldb_private::formatters::LibcxxFunctionSummaryProvider(
  auto default_print_on_exit = llvm::make_scope_exit(
  [&found_wrapped_function, &stream, &member__f_pointer_value]() {
  if (!found_wrapped_function)
  - stream.Printf(" __f_ = %llu", member__f_pointer_value);
  + stream.Printf(" __f_ = %" PRIu64, member__f_pointer_value);
  });
  lldb::addr_t address_after_vtable = member__f_pointer_value + address_size;
  