[PATCH v2] libio: Add test for fopen with an empty ", ccs=" value [BZ #34574]

[Florian Weimer]

* Shamil Abdulaev:

> This goes on top of the fix for CVE-2026-18374.  The test runs the
> reproducer from the bug report, plus "w,ccs=" and "w,ccs=,", and
> expects NULL with errno set to EINVAL.
>
> Signed-off-by: Shamil Abdulaev <ashamil435@gmail.com>

New version is okay.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

Thanks,
Florian