Failure to build release for sparc64

[Chris Ross <cross+netbsd%distal.com@localhost>]

  Crossbuilding on an i386, I was getting a failure in etc/sparc64/ 
bootfs, eventually saying:

#    create  bootfs/boot.fs
nbmakefs: `work' size of 5283840 is larger than the maxsize of 5242880.
*** [boot.fs] Error code 1
1 error
nbmake: stopped in /data/NetBSD/src/distrib/sparc64/bootfs

  This is the sort of thing that occurs periodically in many ports,  
but I hadn't seen anything come across that looked like it might fix  
it.  This happened in sources up to date as of Friday night/Saturday  
morning, and again updated Sunday 05:00ish UTC.  I'm running a build  
again off of sources now (1-Mar 04:22 UTC), but I don't know that I  
saw anything change that I'd expect to fix this.  On brief scan.

  Anyone already working on this?  Just wanted to make sure I didn't  
miss something.  Thanks.

                            - Chris