I propose to change the pack command that's used when creating S/MIME signed and/or S/MIME encrypted archives on Linux from tar to gpgtar.

Reasoning:

• On Windows, gpgtar has always been used, i.e. it seems to be fit for the task.
• On Linux, we use gpgtar (via gpgme) since some time already when creating OpenPGP signed and/or OpenPGP encrypted archives.
• Using tar causes problems, e.g. T8234: Kleopatra: On Linux, creating S/MIME encrypted archive of multiple files for certificate with bad CRL fails with input/output error. This turned out to be a wrong assumption. See T8234#217607.