Why the Mac OS X Nightlies never get built

I discovered (partially) why the Mac OS X nightlies never get built.

A) My cron job apparently only gets run once when the machine is 
rebooted, NOT nightly as it is configured.

B) As far as I can tell, cron passes a *completely* blank environment to 
cron jobs, so not only is the PATH I took the time to set up not 
working, it is acting like PATH=

I have never really needed to do cron jobs on a Mac before now, so I 
don't know if I am running into a common problem, or if something else 
is causing the problems.

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James