message: Add if kernel to Makefile.
diff: @@ -356,6 +356,7 @@ tensorflow/lite/micro/kernels/fully_connected_common.cc \
  tensorflow/lite/micro/kernels/gather.cc \
  tensorflow/lite/micro/kernels/gather_nd.cc \
  tensorflow/lite/micro/kernels/hard_swish.cc \
  +tensorflow/lite/micro/kernels/if.cc \
  tensorflow/lite/micro/kernels/kernel_runner.cc \
  tensorflow/lite/micro/kernels/kernel_util.cc \
  tensorflow/lite/micro/kernels/l2norm.cc \
  