emacs build broken?

[rustom]

I did  (for a emacs 23 build)
$cvs update -dP
$make distclean
make bootstrap
After a lot of grinding it stops at (last few lines)

Generating autoloads for mail/rmailmm.el...
Generating autoloads for mail/rmailmsc.el...
Generating autoloads for mail/rmailout.el...
Generating autoloads for mail/rmailout.el...done
Generating autoloads for mail/rmailsort.el...
Generating autoloads for mail/rmailsum.el...
End of file during parsing
make[3]: *** [autoloads] Error 255
make[3]: Leaving directory `/home/siva/pdsw/emacs/lisp'
make[2]: *** [/home/siva/pdsw/emacs/src/../lisp/loaddefs.el] Error 2
make[2]: Leaving directory `/home/siva/pdsw/emacs/src'
make[1]: *** [src] Error 2
make[1]: Leaving directory `/home/siva/pdsw/emacs'
make: *** [bootstrap] Error 2

When I did downloaded a fresh tar.bz2 of 23.1 it has compiled ok.
So I guess this is a broken build.

So ok... during development builds can break.
My question is how do I do a cvs update (rather than a full download)
and yet stay with relatively stable emacs versions?