message: Update CMake guide for building C library
diff: @@ -154,3 +154,27 @@ add_subdirectory(
  add_executable(minimal minimal.cc)
  target_link_libraries(minimal tensorflow-lite ${CMAKE_DL_LIBS}
  ```
  +
  +## Build TensorFlow Lite C library
  +
  +If you want to build TensorFlow Lite shared library for
  +[C API](https://github.com/tensorflow/tensorflow/blob/master/tensorflow/lite/c/README.md),
  +follow [step 1](#step-1-install-cmake-tool) to
  +[step 3](#step-3-create-cmake-build-directory) first. After that, run the
  +following commands.
  +
  +```sh
  +cmake ../tensorflow_src/tensorflow/lite/c
  +cmake --build . -j
  +```
  +
  +This command generates the following shared library in the current directory.
  +
  +Platform | Library name
  +-------- | -------------------------
  +Linux | libtensorflowlite_c.so
  +macOS | libtensorflowlite_c.dylib
  +Windows | tensorflowlite_c.dll
  +
  +**Note:** You need necessary headers (c_api.h, c_api_experimental.h and
  +common.h) to use the generated shared library.
  