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

Test: treehugger
Change-Id: I73d6ed21520a0c2659826d1c01479917ed9b388d
diff --git a/tests/libs/preinit_getauxval_test_helper.cpp b/tests/libs/preinit_getauxval_test_helper.cpp
index 2a79b97..53d4cc9 100644
--- a/tests/libs/preinit_getauxval_test_helper.cpp
+++ b/tests/libs/preinit_getauxval_test_helper.cpp
@@ -19,7 +19,7 @@
 #include <unistd.h>
 #include <sys/auxv.h>
 
-#include "libs_utils.h"
+#include "CHECK.h"
 
 static unsigned long g_AT_RANDOM;
 static unsigned long g_AT_PAGESZ;