Nullability check for stdlib module.

Bugs: b/245972273
Test: None

Change-Id: Ib33a5359a924c21888f268158c4d7f824740dd55
diff --git a/tests/stdlib_test.cpp b/tests/stdlib_test.cpp
index f507e08..45169e3 100644
--- a/tests/stdlib_test.cpp
+++ b/tests/stdlib_test.cpp
@@ -494,7 +494,10 @@
 TEST(stdlib, system_NULL) {
   // "The system() function shall always return non-zero when command is NULL."
   // http://pubs.opengroup.org/onlinepubs/9699919799/functions/system.html
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnonnull"
   ASSERT_NE(0, system(nullptr));
+#pragma clang diagnostic pop
 }
 
 // https://austingroupbugs.net/view.php?id=1440