Grab either of these:
https://www.busybox.net/downloads/bi...busybox-armv5l
https://www.busybox.net/downloads/bi...busybox-armv7l
Put it in one of the bin dirs, chmod +x, then
busybox-armv7l microcom <someoption?> /dev/ttymcx0
Can't test it myself since I don't have anything hooked to the serial lines.