Disable callstack for mac too.

Bug: 171353386

Test: Builds.
Change-Id: Id8a5cce170682ea43aa641c187c22cb31b6fd017
diff --git a/libutils/RefBase.cpp b/libutils/RefBase.cpp
index 2523097..8e45226 100644
--- a/libutils/RefBase.cpp
+++ b/libutils/RefBase.cpp
@@ -55,7 +55,7 @@
 // case.
 #define DEBUG_REFBASE_DESTRUCTION 1
 
-#if !defined(_WIN32)
+#if !defined(_WIN32) && !defined(__APPLE__)
 // CallStack is only supported on linux type platforms.
 #define CALLSTACK_ENABLED 1
 #else