Fix TensorFlow build on Ubuntu 16.04
Fix TF build error
```
external/eigen_archive/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h:340:167: error: non-constant-expression cannot be narrowed from type 'long long' to 'int' in initializer list [-Wc++11-narrowing]
```
Solution suggested at
@@ -16,6 +16,7 @@ platforms:
# is merged to upstream TensorFlow, it's a temporary workaround for
# https://github.com/bazelbuild/bazel/issues/5365.
- "--cxxopt=--std=c++11"
+ - "--copt=-Wno-c++11-narrowing"
build_targets:
- "//tensorflow/tools/pip_package:build_pip_package"
- "//tensorflow/examples/android:tensorflow_demo"
