Make build rule for //tensorflow/contrib/lite/tools:benchmark_model (#15005)

* Make buid rule for //tensorflow/contrib/lite/tools:benchmark_model

Note that this benchmark_model.cc is not completed yet. It doesn't
load and models.

1. With proper Android SDK and NDK settings in WORKSPACE, we can
   build armeabi-v7a or arm64-v8a binary, e.g.,

   > bazel build --cxxopt='--std=c++11' \
     --crosstool_top=//external:android/crosstool \
     --cpu=arm64-v8a \
     --host_crosstool_top=@bazel_tools//tools/cpp:toolchain \
    //tensorflow/contrib/lite/tools:benchmark_model

2. It's also possible to build this for Linux or OS X, e.g.,

   >  bazel --config opt --cxxopt='--std=c++11' \
     //tensorflow/contrib/lite/tools:benchmark_model