Bug#942558: hurd: should return ENXIO instead of EIEIO in open()

[Shengjing Zhu <zhsj@debian.org>]

Source: hurd
Version: 1:0.9.git20190331-8
Severity: important
Control: affects -1 s6

Dear Maintainer,

When calling open(fifo_fd, O_WRONLY | O_NONBLOCK) on an fifo file, which has
no reader, it should return ENXIO. But on Hurd, it returns EIEIO.

This causes s6 failed to start[1], as it expects an ENXIO.

The behaviour should be consistent with

https://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html

> [ENXIO]
> O_NONBLOCK is set, the named file is a FIFO, O_WRONLY is set,
> and no process has the file open for reading.

[1] it was discussed at
https://www.mail-archive.com/skaware@list.skarnet.org/msg01361.html

-- 
Shengjing Zhu