Tests: use guarded allocator in tests

This helps finding memory leaks in tests.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D8631

tests/gtests/testing/testing_main.cc

@@ -48,6 +48,7 @@ const std::string &flags_test_release_dir()
 
 int main(int argc, char **argv)
 {
+  MEM_use_guarded_allocator();
   MEM_init_memleak_detection();
   testing::InitGoogleTest(&argc, argv);
   BLENDER_GFLAGS_NAMESPACE::ParseCommandLineFlags(&argc, &argv, true);