Include System.CommandLine.NamingConventionBinder as part of source-build

[MichaelSimons]

System.CommandLine.NamingConventionBinder needs to be included in source-build as sourcelink has taken a dependency on it https://github.com/dotnet/sourcelink/blob/main/src/dotnet-sourcelink/dotnet-sourcelink.csproj#L16.

It is currently not part of the sourcebuild.slnf.

[MichaelSimons]

FYI - @ViktorHofer, this is the source of the problem encountered in dotnet/installer#15130