On: "I think that djb redo will turn out to be the Git of build systems."

[Freaky]

FreeBSD has kernel DTrace (off by default), with userspace tracing on its way (in CURRENT). ktrace is a better option there, especially if you want to support other BSD systems as well.

I've used ktrace to help create minimal jail environments, quite handy: http://www.aagh.net/files/mkjail