OK, thanks to Jason Thorpe for the info on db_machdep.c.  I got past that 
glitch...

now, I get this:

making sure the kern library is up to date...
Unknown modifier 'Q'

[about 7 more of the 'Q' messages]

  -I/usr/src/sys/lib/libkern/arch/  -c /usr/src/sys/lib/libkern/adddi3.c
-I/usr/src/sys/lib/libkern/arch/: not found

...and it dies again.  This last line appears to be only a partial line, 
for some reason.  It appears to be trying to execute some makefile 
variable, is my guess.

maybe a makefile error?

thanks for any help,
Jonathan