Disable backtraces on android, which will enable mksnapshot
to build when android is built on tiger.

Change-Id: Idc9bd51a69cf1308fa5ab64862ac6d0b352025af
diff --git a/src/platform-macos.cc b/src/platform-macos.cc
index e379ae2..27f0141 100644
--- a/src/platform-macos.cc
+++ b/src/platform-macos.cc
@@ -278,6 +278,12 @@
 
 
 int OS::StackWalk(Vector<StackFrame> frames) {
+#ifdef ANDROID
+  // For some reason the weak linkage doesn't work when building mksnapshot
+  // for android on macos. Just bail out as if we're on 10.4. We don't need
+  // stack walking for mksnapshot.
+  return 0;
+#else
   // If weak link to execinfo lib has failed, ie because we are on 10.4, abort.
   if (backtrace == NULL)
     return 0;
@@ -309,6 +315,7 @@
   free(symbols);
 
   return frames_count;
+#endif // ANDROID
 }