Fix mac build

Change-Id: I22bf169f15483e54b97d77ff0887cd1fde428af9
diff --git a/runtime/mem_map.cc b/runtime/mem_map.cc
index 6a0c6d6..9fef544 100644
--- a/runtime/mem_map.cc
+++ b/runtime/mem_map.cc
@@ -744,7 +744,9 @@
                           off_t offset,
                           bool low_4gb) {
 #ifdef __LP64__
+#ifndef __APPLE__
   DCHECK_EQ(flags & MAP_32BIT, 0);
+#endif
   // When requesting low_4g memory and having an expectation, the requested range should fit into
   // 4GB.
   if (low_4gb && (