this was not really testing anything before, because it was doing
   sizeof(char*)
which is 4 or 8

Change-Id: I7eccdd3c6ae14a6fabb27202737fdb2fd12663dc
Reviewed-on: https://gerrit.libreoffice.org/60182
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>