Fix PR4007: clang doesn't know  -Werror-foo is the same as -Werror=foo


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@69557 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Preprocessor/if_warning.c b/test/Preprocessor/if_warning.c
index 5fc8c34..5567513 100644
--- a/test/Preprocessor/if_warning.c
+++ b/test/Preprocessor/if_warning.c
@@ -1,4 +1,5 @@
-// RUN: clang-cc %s -Eonly -Werror=undef -verify
+// RUN: clang-cc %s -Eonly -Werror=undef -verify &&
+// RUN: clang-cc %s -Eonly -Werror-undef -verify
 
 extern int x;