Avoid writing to the test directory as it may not be writable.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@217339 91177308-0d34-0410-b5e6-96231b3b80d8

test/SemaCXX/warn-unused-local-typedef-serialize.cpp

 // RUN: %clang -x c++-header -c -Wunused-local-typedef %s -o %t.gch -Werror
-// RUN: %clang -DBE_THE_SOURCE -c -Wunused-local-typedef -include %t %s 2>&1 | FileCheck %s
-// RUN: %clang -DBE_THE_SOURCE -c -Wunused-local-typedef -include %t %s 2>&1 | FileCheck %s
+// RUN: %clang -DBE_THE_SOURCE -c -Wunused-local-typedef -include %t %s -o /dev/null 2>&1 | FileCheck %s
+// RUN: %clang -DBE_THE_SOURCE -c -Wunused-local-typedef -include %t %s -o /dev/null 2>&1 | FileCheck %s
 
 #ifndef BE_THE_SOURCE
 inline void myfun() {