Choosing the targetframework version for debugging

[RobertvanderHulst]

In the released version of the project system, the debug menu shows the frameworks for the startup project and you can choose which framework to run.

When I compile the code from Github, this Framework Menuitem is not visible.
Background:
I am creating a project system for our language and taking this code as an example. I would like to support this too.
I did see the menu point in the menus.vsct file and references to the menu item in the code, but it does not work.