Add regression test

Author: DKLoehr

clang/test/Headers/no-xend.cpp

@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -triple x86_64-pc-win32 \
+// RUN:     -fms-extensions -fms-compatibility -fms-compatibility-version=17.00 \
+// RUN:     -ffreestanding -fsyntax-only -Werror -Wsystem-headers \
+// RUN:     -isystem %S/Inputs/include %s
+
+#include <immintrin.h>
+
+#pragma clang attribute push(__attribute__((target("avx"))), apply_to=function)
+#include <intrin.h>
+#pragma clang attribute pop