Don't build separate bin output for alex.

It has files in /usr/share which reference the bin output.

pkgs/development/haskell-modules/lib.nix

@@ -142,6 +142,8 @@ rec {
   overrideSrc = drv: { src, version ? drv.version }:
     overrideCabal drv (_: { inherit src version; editedCabalFile = null; });
 
+  hasNoBinOutput = drv: overrideCabal drv (drv: { enableSeparateBinOutput = false; });
+
   installOutputs = drv: outputs: overrideCabal drv
     (drv: { outputsToInstall = outputs; });
 }