ms-intrin.cpp: add -Werror to the test

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199450 91177308-0d34-0410-b5e6-96231b3b80d8

test/Headers/ms-intrin.cpp

 // RUN: %clang_cc1 -triple i386-pc-win32 -target-cpu pentium4 \
 // RUN:     -fms-extensions -fms-compatibility -fmsc-version=1700 \
-// RUN:     -ffreestanding -fsyntax-only %s
+// RUN:     -ffreestanding -fsyntax-only -Werror %s
 
 // Intrin.h needs size_t, but -ffreestanding prevents us from getting it from
 // stddef.h.  Work around it with this typedef.