Use import list to hide new System.Exit.die

Starting with GHC 7.10 (and soon GHC HEAD), System.Exit exports the new `die`
which would clash with Cabal's own `die`. See also

  https://ghc.haskell.org/trac/ghc/ticket/9016

For more details.

(cherry picked from commit 322ddbc019bf2386897b9b9be7d534cc0e4d39c1)