treewide: use ocaml.version (#19192)

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

@@ -1,15 +1,12 @@
 { stdenv, fetchzip, which, cryptopp, ocaml, findlib, ocaml_react, ocaml_ssl, libev, pkgconfig, ncurses, ocaml_oasis, ocaml_text, glib, camlp4, ppx_tools }:
 
 let
-  version = "2.5.2";
   inherit (stdenv.lib) optional getVersion versionAtLeast;
-  ocaml_version = getVersion ocaml;
 in
 
-stdenv.mkDerivation {
-
-
+stdenv.mkDerivation rec {
   name = "ocaml-lwt-${version}";
+  version = "2.5.2";
 
   src = fetchzip {
     url = "https://github.com/ocsigen/lwt/archive/${version}.tar.gz";
@@ -21,7 +18,7 @@ stdenv.mkDerivation {
   propagatedBuildInputs = [ ocaml_react ocaml_ssl ocaml_text libev ];
 
   configureFlags = [ "--enable-glib" "--enable-ssl" "--enable-react" "--enable-camlp4"]
-  ++ [ (if versionAtLeast ocaml_version "4.02" then "--enable-ppx" else "--disable-ppx") ];
+  ++ [ (if versionAtLeast ocaml.version "4.02" then "--enable-ppx" else "--disable-ppx") ];
 
   createFindlibDestdir = true;