Hi again,
the workaround which I'm now using is to run devenv.exe:
https://msdn.microsoft.com/en-us/library/b20w810z.aspx
I've modified the original build step to only update the project properties, inserted a step to clean the project, just to be sure, and inserted the 'Run Program' action.
Easier/better workarounds - or even a proper solution - are very welcome.
Nice weekend
Wolfgang