supki figured it out:
os(windows) is true, flag(old-time) is false, so wrong directory dependency is chosen here
it adds build-depends: directory >= 1.2 && < 1.3
which is wrong for ghc-7.4
I'm not sure if there is an easy way to fix this, directory 1.1 needs old-time and I don't think there is a way to say "use directory 1.1 and old-time, or directory >= 1.2 and time" without using a flag like we have done.
You should be able to install it using "cabal install unix-compat -fold-time"
If you can think of another way which works without needing a flag I'll happily accept a patch.