treewide: use ocaml.version (#19192)

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

@@ -1,16 +1,14 @@
 {stdenv, fetchurl, ocaml, findlib, opam}:
 let
   pname = "uunf";
-  version = "0.9.3";
   webpage = "http://erratique.ch/software/${pname}";
-  ocaml_version = (builtins.parseDrvName ocaml.name).version;
 in
 
-assert stdenv.lib.versionAtLeast ocaml_version "3.12";
+assert stdenv.lib.versionAtLeast ocaml.version "3.12";
 
 stdenv.mkDerivation rec {
-
   name = "ocaml-${pname}-${version}";
+  version = "0.9.3";
 
   src = fetchurl {
     url = "${webpage}/releases/${pname}-${version}.tbz";
@@ -28,7 +26,7 @@ stdenv.mkDerivation rec {
   installPhase = ''
     opam-installer --script --prefix=$out ${pname}.install > install.sh
     sh install.sh
-    ln -s $out/lib/${pname} $out/lib/ocaml/${ocaml_version}/site-lib/
+    ln -s $out/lib/${pname} $out/lib/ocaml/${ocaml.version}/site-lib/
   '';
 
   meta = with stdenv.lib; {