Fix build

Make it work with GHC 8.2

tests/Main.hs

@@ -12,6 +12,7 @@ module Main where
 import Control.Monad (when,foldM)
 import Data.List (isPrefixOf,partition,nub)
 import Data.Monoid (Endo(..))
+import Data.Semigroup(Semigroup(..))
 import System.Console.GetOpt
     (getOpt,usageInfo,ArgOrder(..),OptDescr(..),ArgDescr(..))
 import System.Directory

tests/cryptol-test-runner.cabal

@@ -24,7 +24,8 @@ executable cryptol-test-runner
                        directory,
                        HUnit,
                        test-framework,
-                       test-framework-hunit
+                       test-framework-hunit,
+                       semigroups
   GHC-options:         -Wall -O2
   Default-language:    Haskell2010