xamarin-macios/dotnet/package/Microsoft.MacCatalyst.Runtime.maccatalyst-x64/package.csproj

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

  <PropertyGroup>
    <_PlatformName>MacCatalyst</_PlatformName>
    <_RuntimeIdentifier>maccatalyst-x64</_RuntimeIdentifier>
  </PropertyGroup>

  <Import Project="../microsoft.runtime.csproj" />
</Project>