Adds support for building arm64 Android.

runtime/bin/dbg_connection_android.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef BIN_DBG_CONNECTION_ANDROID_H_
 #define BIN_DBG_CONNECTION_ANDROID_H_
 
 #include <arpa/inet.h>
 #include <netdb.h>
 #include <sys/socket.h>
@@ skipping 10 matching lines @@
 
  private:
   static void SetupPollQueue();
   static void HandleEvent(struct epoll_event* event);
   static void Handler(uword args);
 
   // File descriptors for pipes used to communicate with the debugger thread.
   static int wakeup_fds_[2];
 
   // File descriptor for the polling queue.
-  static int epoll_fd_;
+  static intptr_t epoll_fd_;
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // BIN_DBG_CONNECTION_ANDROID_H_