[SBRP] AssemblyVersion is no being set correctly by the generate tooling

[MichaelSimons]

If you run the generate tooling for an existing package in SBRP, compile, and compare the resulting assembly to the original, you will see the new one is no longer versioned correctly, its assembly version is 0.0.0.0

Diffing the generated code, I see the [assembly: AssemblyVersion("a.b.c.d")] was removed.

[MichaelSimons]

cc @andriipatsula, @ViktorHofer

[ViktorHofer]

Yeah that's a reference package source generator bug, I'll take that one. Regressed with dotnet/source-build-reference-packages@98e81d7

[MichaelSimons]

cc @oleksandr-didyk

[ViktorHofer]

I just checked and the following two assembly attributes were lost during the refactoring:

[assembly: ReferenceAssembly]
[assembly: AssemblyVersion("...")]