spec: Explicitly disable userfaultfd_sysctl for mingw

The %meson* macros pass --auto-features=enabled to enable all "auto"
features, which means we have to explicitly disable them.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

libvirt.spec.in

@@ -1452,6 +1452,7 @@ export SOURCE_DATE_EPOCH=$(stat --printf='%Y' %{_specdir}/libvirt.spec)
   -Dstorage_vstorage=disabled \
   -Dstorage_zfs=disabled \
   -Dsysctl_config=disabled \
+  -Duserfaultfd_sysctl=disabled \
   -Dtests=disabled \
   -Dudev=disabled \
   -Dwireshark_dissector=disabled \