Proper handling of ocaml_captures_build_path

[Chris Lamb]

Hi Stéphane,

> Indeed, most of OCaml packages depend on dh-ocaml and include a snippet
> from there. I've added an export of BUILD_PATH_PREFIX_MAP to this
> snippet (as of 1.1.1), which seems to fix the ocaml_captures_build_path
> issue.

Unfortunately, at quick glance I can't seem to be able to reproduce
this. Take, for example, the 2020-01-29 14:02:00 build of belenios in
unstable/amd64:

  https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/diffoscope-results/belenios.html

I you review the .buildinfo file we can see that it was built with the
aforementioned new version of dh-ocaml, ie.:

  dh-ocaml (= 1.1.1),

… but we still see build-path related changes between the two builds:

    camlTool_cmdline__stream_to_list_317():
   -/build/1st/belenios-1.10+dfsg/_build/src/tool/tool_cmdline.ml:28 
   +/build/2/belenios-1.10+dfsg/2nd/_build/src/tool/tool_cmdline.ml:28


Best wishes,

-- 
      o
    ⬋   ⬊      Chris Lamb
   o     o     reproducible-builds.org
    ⬊   ⬋
      o