NOTE: When building OpenPGP-Haskell for the first time, be
sure to first run:
make Data/OpenPGP/Arbitrary.hs
Otherwise, the first build succeeds, but cabal complains
about missing the file on successive builds.
At version 1.6.0, Vincent Hanquez refactored x509 to depend on his
cryptonite library, but this causes type errors due to functions
which expect and return types from the wrong module.