Revert "See if multithreaded dex2oat is causing the Mac OS 10.6 build problems."

This reverts commit 4522989c9c4916582b482b878949c5d76a29daec
diff --git a/src/dex2oat.cc b/src/dex2oat.cc
index fbe55a3..660115c 100644
--- a/src/dex2oat.cc
+++ b/src/dex2oat.cc
@@ -554,10 +554,6 @@
     }
   }
 
-#if defined(__APPLE__)
-  thread_count = 1;
-#endif
-
   if (oat_filename.empty() && oat_fd == -1) {
     Usage("Output must be supplied with either --oat-file or --oat-fd");
   }