Integrate minimal smoke-test during build-time

As part of the MIR review Christian Ehrhardt suggested adding a small smoke-test during build-time [1]:

> #4 only testing in autopkgtests
>
> I'd prefer to have something not as gigantic in build time tests (read = "I agree to not add the huge thing, but something small maybe", just a reasonable sanity check).
> But that isn't a hard requirement if there are good autopkgtests and there are.
> You have lots of good "make the autopkgtest even better" and that might be where the time is indeed spend better now.

The advantage of this is catching major errors early on. A small smoke test like compiling and running a hello world application should be enough; like:

dotnet new console -o HelloWorld
cd HelloWorld
dotnet run

[1] https://bugs.launchpad.net/ubuntu/+source/dotnet6/+bug/2023531/comments/8