Fix Windows build with latest visual c++ + packaging

The current work is fixing the compilation for Windows.

The aim of the MR is to have a NSIS build, that can be generated within the binary-factory (https://binary-factory.kde.org/view/Windows%2064-bit/).

I only did the minimum to fix the compilation now, are the developers ok with the continuation of the packaging (and so I'll continue, else I'll only limit the MR to the compilation fixes)?

Final goal would be to publish on the Windows store (https://phabricator.kde.org/T9575) if developers agree.

Note: I splitted the commits to separate the different fixes, all can be squashed at the end if it is preferable.