fix a bug of the android Makefile for nsync library
authorgdh1995 <gdh1995@qq.com>
Mon, 21 May 2018 06:23:32 +0000 (14:23 +0800)
committergdh1995 <gdh1995@qq.com>
Tue, 22 May 2018 02:52:14 +0000 (10:52 +0800)
commitee03d18c66d74bde4db29f079025ce74d36ad2dc
tree985902be1cc3016b2faccdf44cba3d6124330fea
parenta2e1b4dcbd0ecd310efa2eb258dcbdbcf942af86
fix a bug of the android Makefile for nsync library

NDK doesn't support thread_local variables which require destructors,
so on Android it should use __thread instead.

Observations:
* ProtoBuf and other libraries are not using thread_local on Android.
* In Tensorflow, there's a "thread_local" in code about CUDA,
  which should be safe enough.

More discussions are on https://github.com/android-ndk/ndk/issues/360 .
tensorflow/contrib/makefile/compile_nsync.sh