message: Fix md5sum command not found issue on mac
  Mac doesn't have md5sum command. Use `md5 -r` instead.
diff: @@ -88,7 +88,13 @@ else
  FLATBUFFERS_MD5="aa9adc93eb9b33fa1a2a90969e48baee"
  wget ${FLATBUFFERS_URL} -O /tmp/${ZIP_PREFIX}.zip >&2
  +
  + if ! command -v md5sum &> /dev/null
  + then
  + MD5=`md5 -r /tmp/${ZIP_PREFIX}.zip | awk '{print $1}'`
  + else
  MD5=`md5sum /tmp/${ZIP_PREFIX}.zip | awk '{print $1}'`
  + fi
  if [[ ${MD5} != ${FLATBUFFERS_MD5} ]]
  then
  