Mock libraries are not built with testutils.c, but there's one which
uses VIR_TEST_DEBUG.  But because that debug should be an error, if we
change it, then it will not only be more semantically correct, but mingw
compiler will be happier as well.

It also follows suit with all other mock libraries.

For few other things, used in this file, need libvirt.la to be added
into LIBADD for mingw as well.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>