[xbuild]: Fix 'make test'.
[xbuild]: Fix task batching for <ItemGroup> inside <Target>.

This fixes

	<Target Name="Simple">
		<ItemGroup>
			<Foo Include="A;B" />
			<All Include="%(Foo.Identity)" />
		</ItemGroup>
		<Message Text="ALL: @(All)" />
	</Target>
[make]: Build Facade assemblies in mcs/class/lib/$(PROFILE)/Facades.