I was noticing that sometimes Ctrl-C at the TTY doing a kdesrc-build -p
left a monitor process hanging at 100% CPU, not to mention all the
kdesrc-build processes spamming goodbye messages.

It didn't help that I was doing waitpid on an updater PID when that
updater PID had to be 0 by definition.

Either way, I've verified that the forking going on here shouldn't start
a different process group for the shell session, so ^C is already going
to all of the relevant processes. We just need to make sure to catch the
signal and do the right thing (i.e. exit the child process).