NETSDK1145 - Update KnownAppHostPack AppHostPackVersion

Directory.Build.targets

<Project>
  <!--
  Update AppHostPackVersion for .net core 3.1
  https://docs.microsoft.com/en-gb/dotnet/core/tools/sdk-errors/netsdk1145
  https://developercommunity.visualstudio.com/t/netsdk1145-the-apphost-pack-is-not-installed-error/1513220
  -->
  <ItemGroup>
    <KnownAppHostPack Update="@(KnownAppHostPack)">
      <AppHostPackVersion Condition="'%(TargetFramework)' == 'netcoreapp3.1'">3.1.26</AppHostPackVersion>
    </KnownAppHostPack>
  </ItemGroup>
  <!--
  <Target Name="OutputBeforeProcessFrameworkReferences" BeforeTargets="ProcessFrameworkReferences">
    <Message Importance="high" Text="KnownAppHostPack = %(KnownAppHostPack.AppHostPackVersion)" />
    <Message Importance="high" Text="KnownAppHostPack = %(KnownAppHostPack.TargetFramework)" />
  </Target>
  -->
</Project>

In vcxproj attempting to update the ItemGroup from a .props file failed, seems it was set too soon. Adding directly to the vcxproj file was necessary to add after all .targets imports. Using Directory.Build.targets appears to work as expected.