bug#35521: Mariadb test suite failures on x86_64-linux

[Mark H Weaver]

hydra.gnunet.org has failed to build mariadb on x86_64-linux
twice in a row:

  https://hydra.gnu.org/build/3475081#tabs-buildsteps

The same test failed both times:

> Failure: Failed 1/5075 tests, 99.98% were successful.
> 
> Failing test(s): tokudb_alter_table.hcad_all_add

The same build also failed twice in a row on my Thinkpad X200, and with
the same error each time, although it's a different error than happens
on hydra.gnunet.org.  On my X200, I get this instead:

> Failure: Failed 1/1091 tests, 99.91% were successful.
> 
> Failing test(s): tokudb_bugs.mdev4533

hydra.gnunet.org successfully built mariadb for i686-linux on its first
attempt:

  https://hydra.gnu.org/build/3473640

Here's the coresponding armhf-linux build, which has not yet been
attempted as I write this:

  https://hydra.gnu.org/build/3481309

       Mark