MFH: r528327 sysutils/py-diffoscope: Restore portability of zipinfo call

/dev/stdin is a non-portable non-POSIX extension having different
semantics on different operating systems. zininfo(1) exits with 9 when
/dev/stdin is supplied on FreeBSD. In fact, unzip(1) explicitly documents
that it does not support reading from stdin.

[1] https://lists.reproducible-builds.org/pipermail/diffoscope/2020-March/002632.html

PR: 244750
Submitted by: Michael Osipov <michael.osipov siemens com>

Approved by: ports-secteam (blanket: runtime bugfix)