Update to directory 1.2

`directory-1.2` uses `time` rather than `old-time`, so the type signature of
`getModificationTime` has changed. As a result `TOD` and `getModificationTime`
return different types, and we get the following error.

    Yst/Build.hs:86:44:
        Couldn't match type `ClockTime'
                      with `time-1.4.0.1:Data.Time.Clock.UTC.UTCTime'
        Expected type: IO time-1.4.0.1:Data.Time.Clock.UTC.UTCTime
          Actual type: IO ClockTime
        In the expression: return $ TOD 0 0
        In the second argument of `catch', namely
          `(\ (_ :: SomeException) -> return $ TOD 0 0)'
        In a stmt of a 'do' block:
          destmod <- catch
                       (getModificationTime destpath)
                       (\ (_ :: SomeException) -> return $ TOD 0 0)

I am not sure about the canonical way to fix this. My fix is from trial and
error.