Restrict reference to Microsoft.Windows.SDK.CPP to non-head projects.

Author: Arlodotexe

MultiTarget/PackageReferences/Uwp.props

@@ -4,6 +4,6 @@
     <PackageReference Condition="'$(MultiTargetPlatformIdentifier)' == 'windows'" Include="Microsoft.Windows.CsWinRT" Version="2.1.6" PrivateAssets="all" />
 
     <!-- Temp workaround until next Windows SDK servicing update -->
-    <PackageReference Condition="'$(HasWinUI)' == 'true' AND '$(MultiTargetPlatformIdentifier)' == 'windows'" Include="Microsoft.Windows.SDK.CPP" Version="10.0.26100.2454" PrivateAssets="all" />
+    <PackageReference Condition="'$(HasWinUI)' == 'true' AND '$(MultiTargetPlatformIdentifier)' == 'windows' AND '$(IsDeployableHead)' != 'true'" Include="Microsoft.Windows.SDK.CPP" Version="10.0.26100.2454" PrivateAssets="all" />
   </ItemGroup>
 </Project>