Handling master/stable package differences on CI

[Andreas Cord-Landwehr]

Hey, currently we have different sets of packages available for master and for 
stable branch groups on build.kde.org. Most prominent among them, only master 
branches can build against Qt5.4, but not stable ones (only providing Qt5.3). 
As a more or less result of this, after the branching of Applications 15.04, 
the new stable branch of Rocs started to fail building as it requires Qt5.4.

I am writing this mail mostly as I am unsure how to proceed here, in 
particular with the 15.04 Beta-1 release being close in front of us.

What I currently see:
* Rocs has a hard dependency to Qt5.4 for a reason (since it uses the QtQuick 
Statemachine) and would require considerable code changes to make it work with 
Qt5.3 (well, a "hack" to get it building on build.k.o is possible with only 
requiring Qt5.3, since building and unit tests should pass, yet IMO that sends 
a very wrong message to packagers as the application would fail starting when 
built against Qt5.3)
* It is a reasonable and very good policy that all to be released applications 
should build on CI and I do not want to challenge this.
* I have no idea when (*) the provided packages on the stable branch group 
should be updated. And actually, for some packages (especially KF5), having 
older Qt versions on the stable branch group is good to ensure that building 
does not break when using the minimal requirements.

Cheers,
Andreas

PS:
(*) We currently (AFAIK) do not have a proper policy telling developers/ 
release team how the different configurations of the different CI branch 
groups relate and when they should be bumped