When running darcs record, darcs ends up with a W^X violation in
newCAF() (from the ghc runtime) via system_io_mmap_file_close()
(from devel/hs-mmap). This can only be fixed in the ghc runtime,
which isn't trivial (and I don't want to work on it before I've
updated to ghc-8).
Since the problem is triggered via devel/hs-mmap, which is only
used by devel/darcs, I hope that darcs is the only haskell program
in our tree running into this problem (instead of changing lang/ghc
to link all programs with -z wxneeded).
Problem initially noticed by Francisco de Borja Lopez Rio.
1a68f2146c