Hi Guix,

As part of <https://issues.guix.gnu.org/47704>, it was discovered
some shell scripts in the mariadb package (e.g. wsrep_sst_rsync)
refer to programs *not* by absolute name.

These programs come from iproute, coreutils, gawk, grep
and mariadb itself.  It seems some substitutions are in order.

Some complications:
some of these scripts are only required in certain configurations.
It's not ideal to increase the closure with rsync and xbcrypt if
they turn out not to be needed ...

Greetings,
Maxime.