Now that we don't need to pass "system" arguments anymore, this thing
is *almost* obsolete. (Except for the need to handle assertion
failures, you could just do "nix-instantiate --eval-only ..." on
release.nix.)
derivation evaluate inside the tryEval. This catches cases such as
aufs2-util, which fails due to an assertion in its dependency aufs2.
* Explicitly blacklist "xbursttools" because it gives some
evaluation error in cross-OpenSSL. No idea why, probably due to
some pass-through attribute.
svn path=/nixpkgs/trunk/; revision=23247
