ocamlPackages.menhir: remove unnecessary substitution

pkgs/development/ocaml-modules/menhir/generic.nix

@@ -13,16 +13,14 @@ stdenv.mkDerivation {
   createFindlibDestdir = true;
 
   preBuild = ''
-    #Fix makefiles.
+    # fix makefiles.
     RM=$(type -p rm)
     CHMOD=$(type -p chmod)
-    ENV=$(type -p env)
-    for f in src/Makefile demos/OMakefile* demos/Makefile* demos/ocamldep.wrapper
+    for f in src/Makefile demos/OMakefile* demos/Makefile*
     do
       substituteInPlace $f \
         --replace /bin/rm $RM \
-	--replace /bin/chmod $CHMOD \
-	--replace /usr/bin/env $ENV
+        --replace /bin/chmod $CHMOD
     done
 
     export PREFIX=$out