Remove bytebench port, which has been repo-copied to unixbench
since development seems to continue now and an upgrade has been
published under this new name.
Use ${ECHO_CMD} instead of ${ECHO} where you mean the echo command; the ECHO
macro is set to "echo" by default, but it is set to "true" if make(1) is
invoked with the -s option while ECHO_CMD is always set to the echo command.