Clean up and explain libs_utils.h^WCHECK.h.

Test: treehugger
Change-Id: I73d6ed21520a0c2659826d1c01479917ed9b388d
diff --git a/tests/libs/cfi_test_helper2.cpp b/tests/libs/cfi_test_helper2.cpp
index 11a6036..d7cd495 100644
--- a/tests/libs/cfi_test_helper2.cpp
+++ b/tests/libs/cfi_test_helper2.cpp
@@ -14,10 +14,9 @@
  * limitations under the License.
  */
 
-#include <assert.h>
 #include <dlfcn.h>
 
-#include "libs_utils.h"
+#include "CHECK.h"
 
 int main(void) {
   void* handle;