Fix GCC 4.8 ICE in cc1/cc1plus with -fuse-ld=mcld

Error message reads:

   cc1: internal compiler error: in common_handle_option, at opts.c:1774

Change-Id: I9a6e42811f0ec83d3a6c05a8bb9b1ec0e5a7144a

Author: Andrew Hsieh <andrewhsieh@google.com>
Date:   Thu Nov 7 13:53:59 2013 +0800
Add built-in macro __ANDROID__ for aarch64-linux-android-gcc

This is to match the existing behavior of 32-bit toolchains.
For example in gcc/config/arm/linux-eabi.h it has the following:
  do
  {
    TARGET_BPABI_CPP_BUILTINS();
    GNU_USER_TARGET_OS_CPP_BUILTINS();
    ANDROID_TARGET_OS_CPP_BUILTINS();
  }
  while (false)

I'll try to upstream this patch.

Change-Id: I22aa6ba5a0d7b5c9cd5a314f7079dc1edd2d382c

Author: Ben Cheng <bccheng@google.com>
Date:   Thu Dec 12 11:02:13 2013 -0800