Don't #include <stdio.h> when tests don't need it, or use clang instead of clang-cc when they do.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@89070 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Sema/attr-format_arg.c b/test/Sema/attr-format_arg.c
index 0830951..5f06f4b 100644
--- a/test/Sema/attr-format_arg.c
+++ b/test/Sema/attr-format_arg.c
@@ -1,6 +1,6 @@
 // RUN: clang-cc -fsyntax-only -verify %s
 
-#include <stdio.h>
+int printf(const char *, ...);
 
 const char* f(const char *s) __attribute__((format_arg(1)));