building world via ccache broken?

hey there,
i've been unable to buildworld using ccache for a while.  initially i 
assumed it was due to some incompatibilities on the drm-next branch 
which i was running, but i've since cut over to CURRENT and am still 
having issues.  running "make buildworld" i am running into this exception:

/usr/home/pwright/git/freebsd/lib/libufs/cgroup.c:217:11: error: no 
member named 'fs_metackhash' in 'struct fs'
         if ((fs->fs_metackhash & CK_CYLGRP) != 0) {
              ~~  ^


full exception here:
https://gist.github.com/nomadlogic/30771aacd05d6dbb1c0cbebfb2ef6b61

I am going to re-run this w/o ccache - to verify that this is a ccache 
related issue.  I guess my first question - is anyone else using ccache 
successfully?

thanks in advance!
-pete

-- 
Pete Wright
pete_at_nomadlogic.org
_at_nomadlogicLA