Allow a missing uninstantiated test

BUG=aomedia:2763

Change-Id: I986041a0dd88c2c3868671ad77719669b628eeea
diff --git a/test/variance_test.cc b/test/variance_test.cc
index 95f22ef..b72ac76 100644
--- a/test/variance_test.cc
+++ b/test/variance_test.cc
@@ -1173,6 +1173,7 @@
 }
 
 typedef MseWxHTestClass<MseWxH16bitFunc> MseWxHTest;
+GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(MseWxHTest);
 typedef MainTestClass<Get4x4SseFunc> AvxSseTest;
 typedef MainTestClass<VarianceMxNFunc> AvxMseTest;
 typedef MainTestClass<VarianceMxNFunc> AvxVarianceTest;