mkmk is in the contrib package contrib/mkmk http://man.cat-v.org/plan_9_contrib/1/mkmk
I would say mkmk was an interesting experiment rather than a resounding success. The idea was to simplify re-porting foreign code to plan9 by autogenerating the mkfile from just the C source and some heuristics. Also important to me is that the generated mkfiles should be simple and cleanly formatted. I use an rc(1) script (called 9port) per package which would tidy it and run mkmk with the apropriate args - it somtimes needs a bit of help. The script may then be reused to quickly re-port the latest version of the code to plan9. Examples here: http://plan9.bell-labs.com/sources/contrib/steve/root/sys/src/cmd/mkmk/9port/ The lack of success came when trying to port bigger projects like the Apache portable runtime, or up to date ghostscript. -Steve
