cksum: Fix --check filename escaping for 9.11

[RenjiSann]

This should fix the md5sum-bsd test, which started failing since the 9.11 release, because GNU switched to shell escaping to print filenames

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/retry. tests/tail/retry is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/cksum/md5sum-bsd is no longer failing!
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.
Note: The gnu test tests/tail/tail-n0f is now being skipped but was previously passing.

[sylvestre]

some jobs are failing

[cakebaker]

Congrats! The gnu test tests/cksum/md5sum-bsd is no longer failing!

Kudos, thanks!