[release/3.1] Downgrade packages when building ref/ projects (#3424)

- dotnet/aspnetcore#24944

Author: dougbu

eng/Versions.props

@@ -84,6 +84,14 @@
     <!-- Packages from dotnet/roslyn -->
     <MicrosoftNetCompilersToolsetVersion>3.4.1-beta4-20127-10</MicrosoftNetCompilersToolsetVersion>
   </PropertyGroup>
+
+  <!-- For the targeting pack, always use packages with PatchVersion=0 -->
+  <PropertyGroup Condition=" '$(MSBuildProjectName)' == 'Microsoft.Internal.Extensions.Refs' OR '$(IsReferenceAssemblyProject)' == 'true' ">
+    <SystemDiagnosticsEventLogPackageVersion>$(SystemDiagnosticsEventLogPackageVersion.Split('.')[0]).$(SystemDiagnosticsEventLogPackageVersion.Split('.')[1]).0</SystemDiagnosticsEventLogPackageVersion>
+    <SystemIOPipelinesPackageVersion>$(SystemIOPipelinesPackageVersion.Split('.')[0]).$(SystemIOPipelinesPackageVersion.Split('.')[1]).0</SystemIOPipelinesPackageVersion>
+    <SystemSecurityCryptographyXmlPackageVersion>$(SystemSecurityCryptographyXmlPackageVersion.Split('.')[0]).$(SystemSecurityCryptographyXmlPackageVersion.Split('.')[1]).0</SystemSecurityCryptographyXmlPackageVersion>
+  </PropertyGroup>
+
   <PropertyGroup Label="Dependency version settings">
     <!--
       Win-x64 is used here because we have picked an arbitrary runtime identifier to flow the version of the latest NETCore.App runtime.