title: tensorflow lite add custom op
body: <p>I install tensorflow from source code. As I need to add some OPs in tensorflow lite model, I followed the steps of the tensorflow offical instructions. But in the end, I grep my op name from the libtensorflow-lite.a, and nothing was found. When use the model in my c++ demo, the error is "Didn't find custom op for name 'MatmulCalc' with version 1", however the name can be greped out  in libtensorflow_cc.so after compiling. And the model transfering process is ok.</p>
  
  <p>So my question is 
  how to add new OP in lite, maybe the official steps is not complete.<a href="https://www.tensorflow.org/guide/extend/op" rel="nofollow noreferrer">https://www.tensorflow.org/guide/extend/op</a></p>