Ah, the agony of defeat.
I'm throwing in the towel on this one. I did manage to compile gdb for hppa using the parisc-linux.org code, but when I tried to make the cross debugger for Hurd it wanted Mach headers for some reason.
So I copied my headers over from the Hurd box, and make just blew up into hundreds of errors. Screw it.
I just purchased a hopefully nice old Pentium-100 on Ebay which will be my debugger box. Hope it works!