Make paths from ld.conf absolute

[rlepigre-skylabs-ai]

This fixes #115 by making relative paths contained in a read ld.conf file absolute (by making them relative to the directory holding the ld.conf file). This is necessary for reading the ld.conf file that is installed by OCaml 5.5.0, which on current opam switch contains:

../stublibs
./stublibs
.

Note however that this will lead to the following paths with this PR, since no normalization is performed.

$OPAM_SWTCH_PREFIX/lib/ocaml/../stublibs
$OPAM_SWTCH_PREFIX/lib/ocaml/./stublibs
$OPAM_SWTCH_PREFIX/lib/ocaml/.

I believe this could have implications for parts of the system that deal with installing / uninstalling packages, but it could well be that things are fine if the paths are always consistent. In any case, I'm not sure the install/uninstall features are widely used now that most packages rely on dune.

[dra27]

Thanks for this - you're right that the normalisation is technically a problem for the detection which findlib does when updating ld.conf (not that that is a very common way to use findlib these days, I think - opam, in particular, is not configured that way). There's a commit in #122 which does both this, and the normalisation.

[rlepigre-skylabs-ai]

OK, thanks. Should we just close this PR then?

[dra27]

Closing in favour of implementation in #122