With the help of Marija Cvetkovic, I found another problem with rtcontrib, specific to Linux this time. Apparently, the Linux implementation of the fseeko(3) library call is broken. This means that the recovery (-r) option in rtcontrib will not work with files larger than 2 GB under Linux. It also means that we need to compile rtcontrib with -Dfseeko=fseek for the time being, until they get this fixed. (I wouldn't hold my breath, given how long it's taken them to fix other problems in little-used functions.)
I have added -Dfseeko=fseek to the Linux rmake in makeall in CVS, and I recommend that anyone wishing to use rtcontrib under Linux modify their rmake script manually by adding this define to the MACH="" line there. Then, using the latest rtcontrib.c, you can run "rmake install" in your src/util directory and all should be well.
Sorry for the inconvenience. I didn't think either of these problems was worth a patch release, but I also want rtcontrib to work for those brave souls who are trying it.