Wheels built for deployment target named based on Python build

After having built PySide2 on macOS 10.12 with Python from python.org (which is built with macOS 10.6) and with deploy target 10.7 (--osx-deployment-target=10.7), the generated wheel is called PySide2-5.6-cp27-cp27m-macosx_10_6_intel.whl. I was expecting the wheel to be suffixed with "10.7" (not "10.6") since that was my deploy target.

As suggested in Gitter, the final wheel name could be controlled via setup.py.

I marked this as affecting 5.6, since this branch is the one where you can define --osx-deployment-target right now. But I assume we'll later be able to define this for the 5.9 branch too and then this ticket would apply to 5.9 as well.