It sucks, I know, but GHC just doesn't compile reliably when built with
some -j<n> option. :-( We have build errors because of apparent race
conditions all over the place on Hydra. This causes so much trouble for
users that it's not worth keeping this option enabled, IMHO.
The change was supposed to trigger a re-build to fix a broken GHC binary
on the Hydra build farm, but now it turns out that the cause for the
errors we're seeing isn't GHC: all kinds of (non-Haskell) packages are
broken.
