Heterogeneous gerrit_mac considered harmful

[Stephan Bergmann]

On 07/12/2019 11:37, Stephan Bergmann wrote:
[...]
> Only some unrelated Gerrit changes that happened to do their gerrit_mac 
> builds on other machines failed, see e.g. 
> <https://ci.libreoffice.org/job/gerrit_mac/48648/> on tb57, where: 
> "checking whether Xcode is new enough... yes (9.3.1)".
> 
> It would IMO be ideal if all gerrit_mac machines used the same baseline 
> setup.  Lacking that, please be careful when adding new includes of 
> <o3tl/optional.hxx>, especially in widely used include files.

<https://bugs.documentfoundation.org/show_bug.cgi?id=122218> "After 
Update to 6.1.4 on macOS fonts are blurred on retina display (xcode 10)" 
is another example of how the mix of build environments not only across 
Gerrit Jenkins' gerrit_mac, but also extending to machines doing nightly 
builds and "official" TDF builds, is actively unhelpful:

I had done the change at 
<https://bugs.documentfoundation.org/show_bug.cgi?id=122218#c169> under 
the naive assumption that all relevant build machines use Xcode 11 by 
now.  For Gerrit Jenkins' gerrit_mac builders, this assumption was 
fueled by the fact that of the seven builders 
(<https://ci.libreoffice.org/label/macosx_clang_dbgutil/>), any that are 
not using Xcode 11 (e.g., tb57, see above; which I had meanwhile 
completely forgotten about) are presumably offline for quite a while 
now.  For nightly builds, this assumption was fueled by the fact that 
the master build mentioned at 
<https://bugs.documentfoundation.org/show_bug.cgi?id=122218#c177> was 
apparently done with Xcode 11.

Only when the one-off 6.3.5 build mentioned at 
<https://bugs.documentfoundation.org/show_bug.cgi?id=122218#c177> did 
not match expectations did it become apparent that different build 
environments using different versions of Xcode are involved.