Restore running tests on macOS CI

[Stephan Bergmann]

On 16/05/2020 09:40, Mike Kaganski wrote:
> Currently (I suppose since the redefinition of what plain make call
> does) our CI does not run tests on macOS buildbots. See e.g.
> https://ci.libreoffice.org/job/gerrit_mac/60981/console.
> 
> IMO this is very unfortunate, and has a potential of creating increasing
> number of problems not detected in time and needing much work to
> identify and fix later.
> 
> Is there a plan to restore the tests on macOS buildbots?

The lode checkout had apparently not been manually updated on all the 
relevant machines after 
<https://git.libreoffice.org/lode/+/a8c281cf47e8c162adf89d1cf3b2f9cebe620b29%5E%21/> 
"change buildbot target to 'unitcheck slowcheck'" and 
<https://git.libreoffice.org/lode/+/1d45bc071db5591da774b078bbbeb3cf23289a6d%5E!/> 
"using 'unitcheck slowcheck' should also include the build target".

I have updated tb82 and tb84 now.  tb69 was apparently already new 
enough, while tb57, tb58, tb59, and tb81 are currently offline.