%external encoder prevents clean shutdown

[vitoyucepi]

Describe the bug

output.icecast(%external) starts.
Liquidsoap can't stop without SIGKILL.

Logs

2023/04/25 14:59:27 [radio:3] Starting process
2023/04/25 14:59:27 [radio:3] Connecting mount radio for source@icecast...
2023/04/25 14:59:27 [radio:2] Connection failed: Not_found
2023/04/25 14:59:27 [radio:3] Closing process's stdin
2023/04/25 14:59:27 [radio:3] Process exited with code 0
2023/04/25 14:59:27 [radio:3] Cleaning up process

2023/04/25 15:03:37 [radio:3] Starting process
2023/04/25 15:03:37 [radio:3] Connecting mount radio for source@icecast...
2023/04/25 15:03:37 [radio:3] Connection setup was successful.
2023/04/25 15:03:42 [radio:2] Error while sending data: could not write data to host: Unix.Unix_error(Unix.EPIPE, "write", "")!
2023/04/25 15:03:42 [radio:3] Closing process's stdin
2023/04/25 15:03:42 [radio:3] Process exited with code 0
2023/04/25 15:03:42 [radio:3] Cleaning up process

To Reproduce

Liquidsoap config

encoder = %external(process="lame - -")
output.icecast(
  encoder,
  sine(),
  format = "audio/mpeg",
  host = "icecast",
  port = 8000,
  user = "source",
  password = "hackme",
  mount = "radio"
)

Expected behavior

Version details

• OS: ubuntu:22.04 in docker
• Version: 2.1.4, 2.2.0+git@01129fe

Install method
Deb package from liquidsoap releases at github

Common issues
#3019, #3020