Fails to create a midi file on lilypond 2.21.4

[Mizutori Tetsuya]

The development versions of lilypond-2.21.3-1.mingw and lilypond-2.21.4-1.mingw 
on windows 7 fails to create a midi file.

When compiling any simple input file with \midi{} command, lilypond fails to
create a midi file with the following error message.

> fatal error: cannot create temp file: sample-01.mid.

This error may occur at Midi_stream::Midi_stream class to open a temp file:

---[ in source file lily/midi-stream.cc ]---
Midi_stream::Midi_stream (const string &file_name) {
  tmp_file_name_ = String_convert::form_string ("%s.%8x", file_name.c_str (), 
rand ());
  out_file_ = fopen (tmp_file_name_.c_str (), "wbx");
}
---

I don't know what causes the failure.

-- 
Mizutori Tetsuya