Proper handling of ocaml_captures_build_path

[Chris Lamb]

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Hi Stéphane,

> But to what value should the build path prefix be set to? Two
> possibilities comes to my mind: either some absolute path like
> /usr/src/$srcpkg or just ".".

Until we see more adoption I would not label it as a "best practice"
just yet but the pattern so far has been to set it to ".". For
example, this is exactly what Debian does when adding -ffile-prefix-
map to CFLAGS via dpkg-buildflags(1):

  https://git.dpkg.org/cgit/dpkg/dpkg.git/tree/scripts/Dpkg/Vendor/Debian.pm#n246

> Is there a way that the toolchain automatically sets
> BUILD_PATH_PREFIX_MAP?

I would share your reservations about scalability and would append my
own æsthetic problems with ugly boilerplating.

However, I notice that a "dh-ocaml" package exists and although this
might be for a more narrower use-case (alas I am not an OCaml
developer) this might be both the cleanest solution and moreover the
most pragmatic one; exporting to the environment via debhelper more
generally á la SOURCE_DATE_EPOCH or even by dpkg itself would likely
be more of a difficult ask.


Regards,

-- 
      ,''`.
     : :'  :     Chris Lamb
     `. `'`      lamby at debian.org 🍥 chris-lamb.co.uk
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