tests: don't mock the time() function on mingw

The mingw header define time() as a static inline function and this
causes a duplicate definition build failure. Since we're not using the
LD_PRELOAD at all on Mingw, we ideally wouldn't compile any of the
mock libraries. Rather than change the build system now though, this
just stubs out the offending function.

Reviewed-by: Laine Stump <laine@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

tests/virnetdaemonmock.c

@@ -23,6 +23,7 @@
 
 #define VIR_FROM_THIS VIR_FROM_NONE
 
+#ifndef WIN32
 time_t time(time_t *t)
 {
     const time_t ret = 1234567890;
@@ -30,3 +31,4 @@ time_t time(time_t *t)
         *t = ret;
     return ret;
 }
+#endif