Refer to the 'odoc' binary by default

Refering to './_build/default/src/odoc/bin/main.exe' is not useful when
running the driver with 'dune exec'.

Author: Julow

src/driver/odoc.ml

@@ -9,9 +9,7 @@ let index_filename = "index.odoc-index"
 
 type compile_deps = { digest : Digest.t; deps : (string * Digest.t) list }
 
-(* This is the just-built odoc binary *)
-let default = "./_build/default/src/odoc/bin/main.exe"
-let odoc = ref (Cmd.v default)
+let odoc = ref (Cmd.v "odoc")
 
 let compile_deps f =
   let cmd = Cmd.(!odoc % "compile-deps" % Fpath.to_string f) in

src/driver/odoc.mli

@@ -5,7 +5,6 @@ val id_of_fpath : Fpath.t -> id
 
 val index_filename : string
 
-val default : string
 val odoc : Bos.Cmd.t ref
 
 type compile_deps = { digest : Digest.t; deps : (string * Digest.t) list }

src/driver/odoc_driver.ml

@@ -499,7 +499,7 @@ let render_stats env nprocs =
 
 let run libs verbose packages_dir odoc_dir odocl_dir html_dir stats nb_workers
     odoc_bin voodoo package_name blessed dune_style =
-  Odoc.odoc := Bos.Cmd.v odoc_bin;
+  Option.iter (fun odoc_bin -> Odoc.odoc := Bos.Cmd.v odoc_bin) odoc_bin;
   let _ = Voodoo.find_universe_and_version "foo" in
   Eio_main.run @@ fun env ->
   Eio.Switch.run @@ fun sw ->
@@ -594,7 +594,7 @@ let nb_workers =
 
 let odoc_bin =
   let doc = "Odoc binary to use" in
-  Arg.(value & opt string Odoc.default & info [ "odoc" ] ~doc)
+  Arg.(value & opt (some string) None & info [ "odoc" ] ~doc)
 
 let packages_dir =
   let doc = "Packages directory under which packages should be output." in