dune_2: init at 2.1.0

Changelog:
- https://github.com/ocaml/dune/releases/tag/2.0.0
- https://github.com/ocaml/dune/releases/tag/2.0.1
- https://github.com/ocaml/dune/releases/tag/2.1.0

pkgs/development/tools/ocaml/dune/2.nix

@@ -0,0 +1,31 @@
+{ stdenv, fetchurl, ocaml, findlib }:
+
+if stdenv.lib.versionOlder ocaml.version "4.07"
+then throw "dune is not available for OCaml ${ocaml.version}"
+else
+
+stdenv.mkDerivation rec {
+  pname = "dune";
+  version = "2.1.0";
+
+  src = fetchurl {
+    url = "https://github.com/ocaml/dune/releases/download/${version}/dune-${version}.tbz";
+    sha256 = "1hf8c0djx2v1jpjba0z096gw6qdr0igsljrf0qh0ggphg9valsmj";
+  };
+
+  buildInputs = [ ocaml findlib ];
+
+  buildFlags = "release";
+
+  dontAddPrefix = true;
+
+  installFlags = [ "PREFIX=${placeholder "out"}" "LIBDIR=$(OCAMLFIND_DESTDIR)" ];
+
+  meta = {
+    homepage = "https://dune.build/";
+    description = "A composable build system";
+    maintainers = [ stdenv.lib.maintainers.vbgl stdenv.lib.maintainers.marsam ];
+    license = stdenv.lib.licenses.mit;
+    inherit (ocaml.meta) platforms;
+  };
+}