[build] Split stdlib to it's own opam package.

We introduce a new package structure for Coq:

- `coq-core`: Coq's OCaml tools code and plugins
- `coq-stdlib`: Coq's stdlib [.vo files]
- `coq`: meta-package that pulls `coq-{core,stdlib}`

This has several advantages, in particular it allows to install Coq
without the stdlib which is useful in several scenarios, it also open
the door towards a versioning of the stdlib at the package level.

The main user-visible change is that Coq's ML development files now
live in `$lib/coq-core`, for compatibility in the regular build we
install a symlink and support both setups for a while.

Note that plugin developers and even `coq_makefile` should actually
rely on `ocamlfind` to locate Coq's OCaml libs as to be more robust.

There is a transient state where we actually look for both
`$coqlib/plugins` and `$coqlib/../coq-core/plugins` as to support
the non-ocamlfind plus custom variables.

This will be much improved once #13617 is merged (which requires this
PR first), then, we will introduce a `coq.boot` library so finally
`coqdep`, `coqchk`, etc... can share the same path setup code.

IMHO the plan should work fine.

1 files changed, 9 insertions, 1 deletions

diff --git a/tools/coqdep.ml b/tools/coqdep.ml
index 2177da0c75..f1dbac889b 100644
--- a/tools/coqdep.ml
+++ b/tools/coqdep.ml
@@ -97,8 +97,16 @@ let coqdep () =
   if not !option_boot then begin
     Envars.set_coqlib ~fail:(fun msg -> raise (CoqlibError msg));
     let coqlib = Envars.coqlib () in
+    let coq_plugins_dir = CPath.choose_existing
+      [ CPath.make [ coqlib; "plugins" ]
+      ; CPath.make [ coqlib; ".."; "coq-core"; "plugins" ]
+      ] |> function
+    | None ->
+      CErrors.user_err (Pp.str "coqdep: cannot find plugins directory\n");
+    | Some f -> (f :> string)
+    in
     add_rec_dir_import add_coqlib_known (coqlib//"theories") ["Coq"];
-    add_rec_dir_import add_coqlib_known (coqlib//"plugins") ["Coq"];
+    add_rec_dir_import add_coqlib_known (coq_plugins_dir) ["Coq"];
     let user = coqlib//"user-contrib" in
     if Sys.file_exists user then add_rec_dir_no_import add_coqlib_known user [];
     List.iter (fun s -> add_rec_dir_no_import add_coqlib_known s [])