Occasional failing license check

Occasionally the license check fails with the agent failing to install the qtbase source archive.

This appears to be a race condition, as it works sometimes.

The best theory at this point is that when it works, one of the depending build items is responsible for building qtbase and that would ensure the presence of the source archive. But if the license checking test item gets to work before that, then nothing is in place to ensure the creation of the qtbase source archive.

The proposed solution would be to extend the code that ensures the presense of source archives to also include the sources of the dependencies, as that is also how the license checker adds the installSourceArchive instruction.