This is a continuation of CSHARP-2088.
The sourceLink github page says:

Set EmbedUntrackedSources to true to instruct the build system to embed project source files that are not tracked by the source control or imported from a source package to the generated PDB.

At the very least this option affects adding files like "AssemblyInfo.cs" and "AssemblyAttributes.cs", that are not under source control, to the .pdb files.
However we're not sure that settings this option is 100% safe in all possible cases. So we postpone this change until we will figure it out (in the scope of this ticket).

Avoiding this option also leads to warning in a package description:

so it's probably better to solve it in one or another way.