ocamlbuild vs INCLUDE: how to copy snippets into _build/ ?

[Stefano Zacchiroli <zack@upsilon.cc>]

I'm using ocamlbuild and camlp4oof to exploit the INCLUDE syntax
extension, that is have camlp4 expand in the obvious way stuff like:

  INCLUDE "some/relative/path/snippet.mli"

The path passed to INCLUDE is relative to the including file, but with
ocamlbuild I've a problem. Namely, the snippet is not copied inside
the appropriate subdir of _build, and camlp4 correctly fails with
something like:

  File "some/relative/path/snippet.mli", line 52, characters 0-3:
  I/O error: "some/relative/path/snippet.mli: No such file or directory"
  Preprocessing error on file src/foo/bar/including.mli
  Command exited with code 2.

The snippet is not otherwise processed by the OCaml toolchain, it is
just meant to be INCLUDEd.

How can I tell ocamlbuild to copy into the _build/ directory my
snippets?

My reading of the manual doesn't hint me to any useful tag ...

TIA,
Cheers.

-- 
Stefano Zacchiroli -*- PhD in Computer Science \ PostDoc @ Univ. Paris 7
zack@{upsilon.cc,pps.jussieu.fr,debian.org} -<>- http://upsilon.cc/zack/
Dietro un grande uomo c'è sempre /oo\ All one has to do is hit the right
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