Instead, use the generic package override mechanism to use packages
from earlier bootstrap phases.
* Don't rely on the existence of attributes such as
`stdenv.coreutils'.
svn path=/nixpkgs/trunk/; revision=22991
probably be a bit tricky, due to sendmail "compatibility" (postfix makes
a symlink to "sendmail", so programs will keep on working).
svn path=/nixpkgs/trunk/; revision=5030