When CONFIG_USER_RETURN_NOTIFIER is set, we need to link
kernel/user-return-notifier.o.
Signed-off-by: NAvi Kivity <avi@redhat.com>
LKML-Reference: <1256473485-23109-1-git-send-email-avi@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>