How to pack a Roslyn source generator and another dependency into a single package?

[just-ero]

Hello, I would like to pack a Roslyn source generator that I wrote along with another project containing the attributes for said generator into one package. The source generator project does not depend on the other project, as recommended to me by the Roslyn team.

I have decided to create a third project capturing these two projects:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>netstandard2.0</TargetFramework>

    <IncludeBuildOutput>false</IncludeBuildOutput>
    <IsPackable>true</IsPackable>
    <NoWarn>$(NoWarn);NU5128</NoWarn>
  </PropertyGroup>

  <ItemGroup>
    <ProjectReference Include="$(SrcPath)\MyProject.SourceGenerators\MyProject.SourceGenerators.csproj"
                      PrivateAssets="all" />
    <ProjectReference Include="$(SrcPath)\MyProject.SourceGenerators.Core\MyProject.SourceGenerators.Core.csproj"
                      PrivateAssets="all" />
  </ItemGroup>

  <ItemGroup>
    <None Include="$(OutputPath)\MyProject.SourceGenerators.dll"
          Pack="true" PackagePath="analyzers/dotnet/cs"
          Visible="false" />

    <None Include="$(OutputPath)\MyProject.SourceGenerators.Core.dll"
          Pack="true" PackagePath="lib/netstandard2.0" />
  </ItemGroup>

</Project>

However, when I attempt to consume the resulting package, NuGet tries to fetch MyProject.SourceGenerators and MyProject.SourceGenerators.Core as individual packages themselves.

Why? What am I doing wrong? How do I fix this?