[X86] Remove the mm_malloc.h include guard hack from the X86 builtins tests

The X86 clang/test/CodeGen/*builtins.c tests define the mm_malloc.h include
guard as a hack for avoiding its inclusion (mm_malloc.h requires a hosted
environment since it expects stdlib.h to be available - which is not the case
in these internal clang codegen tests).
This patch removes this hack and instead passes -ffreestanding to clang cc1.

Differential Revision: https://reviews.llvm.org/D24825

llvm-svn: 282581
diff --git a/clang/test/CodeGen/sse2-builtins.c b/clang/test/CodeGen/sse2-builtins.c
index 91fa737..48c7036 100644
--- a/clang/test/CodeGen/sse2-builtins.c
+++ b/clang/test/CodeGen/sse2-builtins.c
@@ -1,8 +1,6 @@
-// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin -target-feature +sse2 -emit-llvm -o - -Wall -Werror | FileCheck %s
-// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin -target-feature +sse2 -fno-signed-char -emit-llvm -o - -Wall -Werror | FileCheck %s
+// RUN: %clang_cc1 -ffreestanding %s -triple=x86_64-apple-darwin -target-feature +sse2 -emit-llvm -o - -Wall -Werror | FileCheck %s
+// RUN: %clang_cc1 -ffreestanding %s -triple=x86_64-apple-darwin -target-feature +sse2 -fno-signed-char -emit-llvm -o - -Wall -Werror | FileCheck %s
 
-// Don't include mm_malloc.h, it's system specific.
-#define __MM_MALLOC_H
 
 #include <x86intrin.h>