Fix build errorr

Rx.NET/Source/src/System.Reactive/System.Reactive.csproj

@@ -188,7 +188,7 @@
     <None Include="build\_._" PackagePath="buildTransitive\net5.0;buildTransitive\net5.0-windows10.0.19041" Pack="true" />
     <None Include="build\System.Reactive.targets" PackagePath="buildTransitive\netcoreapp3.1" Pack="true" />
     <None Include="build\System.Reactive.targets" PackagePath="build\netcoreapp3.1" Pack="true" />
-	<None Include="build\System.Reactive.net5.0-windows.targets" PackagePath="build\net5.0-windows\$(PackageId).targets;buildTransitive\net5.0-windows\$(PackageId).targets" Pack="true" />
+	<None Include="build\System.Reactive.net5.0-windows.targets" PackagePath="build\net5.0-windows7\$(PackageId).targets;buildTransitive\net5.0-windows7\$(PackageId).targets" Pack="true" />
     <None Include="Linq\QbservableEx.NAry.cs">
       <DesignTime>True</DesignTime>
       <AutoGen>True</AutoGen>
@@ -200,4 +200,4 @@
     <Service Include="{508349b6-6b84-4df5-91f0-309beebad82d}" />
   </ItemGroup>
 
-</Project>
+</Project>