Call (camlp4 -where) instead of (ocamlfind query camlp4) for camlp4di…

…r setup

This supersedes the ocamlfind-dependent logic of ocaml/ocaml#117,
which raised warning messages in an ocamlfind-less setting.

Changes

@@ -18,8 +18,8 @@ OCamlbuild NEXT_RELEASE
 - Changed OCamlbuild's license to LGPLv2 with static linking exception.
 - OGPR#219: speedup target-already-built builds
   (ygrek)
-- MPR#6605, OGPR#117: use ocamlfind, if available, to discover camlp4 path
-  (Vincent Laporte)
+- MPR#6605, OGPR#117: un-hardcode camlp4 library path
+  (Vincent Laporte and Gabriel Scherer)
 - #20: add -dot and -man-related ocamldoc options
   (Gabriel Scherer)
 - #10, PR#21: Fix manpages generation: properly pass the "manpage" tag.

src/ocaml_specific.ml

@@ -748,14 +748,13 @@ ocaml_lib ~extern:true ~dir:"+ocamldoc" "ocamldoc";;
 ocaml_lib ~extern:true ~dir:"+ocamlbuild" ~tag_name:"use_ocamlbuild" "ocamlbuildlib";;
 
 let camlp4dir =
-  Findlib.(
-    try
-      if sys_command "sh -c 'ocamlfind list >/dev/null' 2>/dev/null" != 0
-      then raise (Findlib_error Cannot_run_ocamlfind);
-      (query "camlp4").location
-    with Findlib_error _ ->
-      "+camlp4"
-  );;
+  let where cmd =
+    (* may raise a Failure exception *)
+    String.chomp
+      (My_unix.run_and_read
+         (cmd ^ " -where 2>/dev/null")) in
+  try where "camlp4" with _ -> "+camlp4"
+;;
 
 ocaml_lib ~extern:true ~dir:camlp4dir ~tag_name:"use_camlp4" "camlp4lib";;
 ocaml_lib ~extern:true ~dir:camlp4dir ~tag_name:"use_old_camlp4" "camlp4";;