message: micro: fix Arduino build for FILL
  Fix the Arduino build for fill by adding the header in Lite with
  the reference implementation to MICROLITE_CC_HDRS in the micro
  Makefile.
diff: @@ -410,6 +410,7 @@ tensorflow/lite/kernels/internal/reference/depthwiseconv_float.h \
  tensorflow/lite/kernels/internal/reference/depthwiseconv_uint8.h \
  tensorflow/lite/kernels/internal/reference/dequantize.h \
  tensorflow/lite/kernels/internal/reference/exp.h \
  +tensorflow/lite/kernels/internal/reference/fill.h \
  tensorflow/lite/kernels/internal/reference/floor.h \
  tensorflow/lite/kernels/internal/reference/fully_connected.h \
  tensorflow/lite/kernels/internal/reference/hard_swish.h \
  