Only use Microsoft.Windows.SDK.CPP on modern .NET

Author: Arlodotexe

MultiTarget/PackageReferences/Uwp/Microsoft.Windows.SDK.CPP.props

@@ -2,7 +2,7 @@
 	<!-- Condition must be on a <When> statement in its own file for this to work in Visual Studio. https://stackoverflow.com/a/16557059 -->
 	<Choose>
     <!-- Temp workaround until next Windows SDK servicing update -->
-		<When Condition="'$(HasWinUI)' == 'true'" >
+		<When Condition="'$(HasWinUI)' == 'true' AND '$(MultiTargetPlatformIdentifier)' == 'windows'" >
 			<ItemGroup>
 				<PackageReference Include="Microsoft.Windows.SDK.CPP" Version="10.0.26100.2454" PrivateAssets="all" />
 			</ItemGroup>