Firefox Build Problem

I have been having the following problem when trying to build Firefox
on OS X.  Does anybody have any ideas what might be wrong?

error: file '../../toolkit/locales/en-US/chrome/necko/contents.rdf'
doesn't exist at ../../config/make-jars.pl line 418.
make[4]: *** [libs] Error 2
make[3]: *** [libs] Error 2
make[2]: *** [tier_9] Error 2
make[1]: *** [default] Error 2
make: *** [build] Error 2


I was able to build Firefox with no problems until about a month ago.
This is trying to build the AVIARY branch.  I am using all of the same
ac_options as the official nightly builds from Mozilla.

Thanks,
Jeff