buildDunePackage: new support function; use it to refactor some OCaml derivations

pkgs/development/ocaml-modules/hex/default.nix

@@ -1,34 +1,25 @@
-{ stdenv, fetchurl, ocaml, findlib, dune, cstruct }:
+{ stdenv, fetchurl, buildDunePackage, cstruct }:
 
-if !stdenv.lib.versionAtLeast ocaml.version "4.02"
-then throw "hex is not available for OCaml ${ocaml.version}"
-else
+buildDunePackage rec {
+  pname = "hex";
+  version = "1.2.0";
 
-let version = "1.2.0"; in
-
-stdenv.mkDerivation {
-  name = "ocaml${ocaml.version}-hex-${version}";
+  minimumOCamlVersion = "4.02";
 
   src = fetchurl {
-    url = "https://github.com/mirage/ocaml-hex/releases/download/v1.2.0/hex-1.2.0.tbz";
+    url = "https://github.com/mirage/ocaml-${pname}/releases/download/v${version}/hex-${version}.tbz";
     sha256 = "17hqf7z5afp2z2c55fk5myxkm7cm74259rqm94hcxkqlpdaqhm8h";
   };
 
   unpackCmd = "tar -xjf $curSrc";
 
-  buildInputs = [ ocaml findlib dune ];
   propagatedBuildInputs = [ cstruct ];
-
-  buildPhase = "dune build -p hex";
   doCheck = true;
-  checkPhase = "jbuilder runtest";
-  inherit (dune) installPhase;
 
   meta = {
     description = "Mininal OCaml library providing hexadecimal converters";
     homepage = https://github.com/mirage/ocaml-hex;
     license = stdenv.lib.licenses.isc;
     maintainers = with stdenv.lib.maintainers; [ vbgl ];
-    platforms = ocaml.meta.platforms or [];
   };
 }