[PATCH] posix: Fix system error return value [BZ #25715]

[Florian Weimer]

* Stefan Liebler via Libc-alpha:

> I've got two test fails as shown below on my Fedora 31/30 (s390x, 
> x86_64) machines. I assume the error-messages differs depending on the 
> used shell?

Looks like it.  It may be possible to turn this test into a container
test, so that the minimal shell implementation from
support/shell-container.c is used, which delivers consistent behavior.