Graph cycles through ---- audio/squeezebox builds forever

[John Marino <marino%netbsd.org@localhost>]

I've got a package (audio/squeezebox) that must have a circular 
dependency somewhere.  It builds forever and would fill the disk if not 
stopped.  Unfortunately, when I kill the build Tinderbox cleans ups most 
of the logs.  I could get them with another build.

One log survived that lists dependencies and it starts with the words 
"Graph cycles through " and then indicates some perl module.  There are 
6 lines (3 unique, repeated twice).  Many lines later, more "Graph 
cycles through" appears in the log.

What does do these words mean?
Is this type of build loop common?
This kind of thing is dangerous, I can't leave the machine building by 
itself if there are multiple packages in the repository that can do this.

John