Don't include malloc.h on MacOS

Thus unbreaking the Mac build once again.

Test: Build AOSP, Treehugger
Bug: 111447610
Change-Id: Icceb1f2726f65e1889b7c3a460cccb8a80a3ebda
diff --git a/runtime/gc/heap.cc b/runtime/gc/heap.cc
index 77254ce..f2c924a 100644
--- a/runtime/gc/heap.cc
+++ b/runtime/gc/heap.cc
@@ -17,7 +17,9 @@
 #include "heap.h"
 
 #include <limits>
+#if defined(__BIONIC__) || defined(__GLIBC__)
 #include <malloc.h>  // For mallinfo()
+#endif
 #include <memory>
 #include <vector>