bug#59616: Texinfo 6.7 test hangs on i586-gnu (GNU/Hurd)

["Ludovic Courtès" <ludo@gnu.org>]

The ‘t/malformed-split.sh’ test of Texinfo 6.7 hangs on GNU/Hurd (in a
childhurd) as of commit 78f03567f44f704dfbc03cb64368aa42a01e78ad.

The test invokes its ‘pseudotty’ program, which creates a
pseudo-terminal using ‘posix openpt’.  That call fails when not running
as root in a childhurd:

--8<---------------cut here---------------start------------->8---
task109(pid14826)-> 4205 (227424 0 0);
  75<--117(pid14826)->io_write_request ("./pseudotty: " -1)./pseudotty:  = 0 13
  75<--117(pid14826)->io_write_request ("getting pty master fd" -1)getting pty master fd = 0 21
  75<--117(pid14826)->io_write_request ("\n" -1)
 = 0 1
task109(pid14826)-> 4205 (227424 0 0);
task109(pid14826)-> 4205 (227424 0 0);
  86<--120(pid14826)->dir_lookup ("dev/ptyp0" 3 0) = 0x4000000d (Permission denied) 
  86<--120(pid14826)->dir_lookup ("dev/ptyp1" 3 0) = 0x40000010 (Device or resource busy) 
  86<--120(pid14826)->dir_lookup ("dev/ptyp2" 3 0) = 0x4000000d (Permission denied) 
  86<--120(pid14826)->dir_lookup ("dev/ptyp3" 3 0) = 0x40000002 (No such file or directory) 
task109(pid14826)-> 4205 (227424 0 0);
task109(pid14826)-> 4205 (227424 0 0);
  118<--122(pid14826)->proc_mark_exit_request (256 0) = 0 
task109(pid14826)-> 4205 (227424 0 0);
task109(pid14826)-> 2008 () = 0 
Child 14826 exited with 1
--8<---------------cut here---------------end--------------->8---

The childhurd only has this:

--8<---------------cut here---------------start------------->8---
ludo@childhurd /tmp/guix-build-texinfo-6.7.drv-0/texinfo-6.7/info$ ls -l /dev/ptyp*
crw--w---- 1 root tty  0, 0 Nov 26 16:05 /dev/ptyp0
crw--w---- 1 ludo tty  0, 0 Nov 26 16:05 /dev/ptyp1
crw------- 1 root root 0, 0 Nov 26 16:05 /dev/ptyp2
--8<---------------cut here---------------end--------------->8---

Ludo’.