In theory we support Qt 5.6 (because of SailfishOS) but in practice we are not checking that in the CI so probably we broke the compatibility long ago. Also, I don't think anyone is using this code in SailfishOS, so we can greatly simplify the code by requiring Qt 5.15 or later.
We use kdeconnect-version.h in several places and therefore it needs to be in the include path. We currently do this by setting target_include_path in a few places. Replace this with an interface library that we can link against that sets up the correct include path. IMO it is cleaner this way.
Ported using KDELibs4Support, for a smaller delta, so we can keep
developing on master until we decide not to.
At the moment, it builds and installs but tests don't pass because
of a QCA2 initialization problem I didn't manage to debug yet.
CCMAIL: kdeconnect@kde.org
