Make this fix Linux-specific.

llvm-svn: 54551
diff --git a/llvm-gcc-4.2/gcc/limitx.h b/llvm-gcc-4.2/gcc/limitx.h
index b8033c0..f801c99 100644
--- a/llvm-gcc-4.2/gcc/limitx.h
+++ b/llvm-gcc-4.2/gcc/limitx.h
@@ -7,8 +7,11 @@
 #include "syslimits.h"
 #endif
 #ifdef _GCC_NEXT_LIMITS_H
-/* LLVM LOCAL Fix for Linux builds */
+/* LLVM LOCAL begin Fix for Linux builds */
+#ifdef __linux__
 #define _GCC_LIMITS_H_
+#endif
+/* LLVM LOCAL end Fix for Linux builds */
 #include_next <limits.h>
 #undef _GCC_NEXT_LIMITS_H
 #endif