fix diff build.

build/ApiDiff.props

@@ -6,7 +6,10 @@
   </PropertyGroup>
     <ItemGroup>
       <PackageDownload Include="Avalonia" Version="[$(ApiContractPackageVersion)]" />
+      <PackageDownload Include="Avalonia.Desktop" Version="[$(ApiContractPackageVersion)]" />
+      <PackageDownload Include="Avalonia.Skia" Version="[$(ApiContractPackageVersion)]" />
+      <PackageDownload Include="Avalonia.Remote.Protocol" Version="[$(ApiContractPackageVersion)]" />      
       <PackageReference Include="Microsoft.DotNet.ApiCompat" Version="5.0.0-beta.20364.3" PrivateAssets="All" />
-      <ResolvedMatchingContract Include="$(NuGetPackageRoot)\$(NugetPackageName)\$(ApiContractPackageVersion)\lib\netstandard2.0\$(AssemblyName).dll" />
+    <ResolvedMatchingContract Include="$(NuGetPackageRoot)\$(NugetPackageName)\$(ApiContractPackageVersion)\lib\netstandard2.0\$(AssemblyName).dll" />
     </ItemGroup>
 </Project>

src/Avalonia.Base/ApiCompatBaseline.txt

@@ -0,0 +1,3 @@
+Compat issues with assembly Avalonia.Base:
+MembersMustExist : Member 'public void Avalonia.Threading.AvaloniaSynchronizationContext..ctor()' does not exist in the implementation but it does exist in the contract.
+Total Issues: 1

src/Markup/Avalonia.Markup.Xaml.Loader/Avalonia.Markup.Xaml.Loader.csproj

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
     <IsPackable>true</IsPackable>
+    <PackageId>Avalonia.Markup.Xaml.Loader</PackageId>
   </PropertyGroup>
   <Import Project="IncludeXamlIlSre.props" />
   <ItemGroup>