Fix race condition in subprocess runner

stdin, stdout, and stderr being closed does not necessarily imply that the process has exited, although it usually does. Still need to explicitly wait for it to terminate after the I/O loop. This matches what the stdlib `subprocess.Popen._communicate` does as well.

codearchiver/subprocess.py

@@ -66,6 +66,7 @@ def run_with_log(args, *, check = True, input = None, **kwargs):
 					stdout.append(data)
 	if stderrBuf:
 		_logger.info(stderrBuf.decode('utf-8'))
+	p.wait()
 	assert p.poll() is not None
 	if input is not None and stdinOffset < len(input):
 		_logger.warning(f'Could not write all input to the stdin pipe (wanted to write {len(input)} bytes, only wrote {stdinOffset})')