bison: Don't run the tests

All this accomplishes is to make bison depend on flex, which in turn
depends on bison.  (So as a result, during the stdenv bootstrap, bison
gets built 6 (!) times.)

pkgs/development/tools/parsing/bison/3.x.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, m4, perl, flex }:
+{ stdenv, fetchurl, m4, perl }:
 
 stdenv.mkDerivation rec {
   name = "bison-3.0.2";
@@ -8,11 +8,9 @@ stdenv.mkDerivation rec {
     sha256 = "1vc17y6242jlwp0gdj7wsim3nvc1ws7q3j0v3065nz8g9hd9vwnd";
   };
 
-  nativeBuildInputs = [ m4 perl ] ++ stdenv.lib.optionals doCheck [ flex ];
+  nativeBuildInputs = [ m4 perl ];
   propagatedBuildInputs = [ m4 ];
 
-  doCheck = flex != null;
-
   meta = {
     homepage = "http://www.gnu.org/software/bison/";
     description = "GNU Bison, a Yacc-compatible parser generator";