Fix build of the test suite

    Preprocessing test suite 'tests' for alex-3.0.5...

    test.hs:1:1:
        Could not find module `Prelude'
        It is a member of the hidden package `base'.
        Perhaps you need to add `base' to the build-depends in your .cabal file.
        It is a member of the hidden package `haskell98-2.0.0.2'.
        Perhaps you need to add `haskell98' to the build-depends in your .cabal file.
        It is a member of the hidden package `haskell2010-1.1.1.0'.
        Perhaps you need to add `haskell2010' to the build-depends in your .cabal file.
        Use -v to see a list of the files searched for.