Merge pull request #31891 from weshaggard/AddPackageBuilds

Add Microsoft.NETCore.Platforms to the package build list

Author: weshaggard

src/packages.builds

@@ -23,6 +23,9 @@
     <Project Include="$(MSBuildThisFileDirectory)..\pkg\Microsoft.Private.CoreFx.NETCoreApp\Microsoft.Private.CoreFx.NETCoreApp.builds">
       <AdditionalProperties>$(AdditionalProperties)</AdditionalProperties>
     </Project>
+    <Project Include="$(MSBuildThisFileDirectory)..\pkg\Microsoft.NETCore.Platforms\Microsoft.NETCore.Platforms.builds">
+      <AdditionalProperties>$(AdditionalProperties)</AdditionalProperties>
+    </Project>
     <!--
       In general we are servicing 2.x library packages from release/2.1 branch so only add library packages
       to this build if they contain unique 2.2 features. If they are added here you need to ensure their