Expected Behavior

dune-site should work when used in a package installed by opam.
In my opinion the destination directory given by dune-site should always return exactly one directory:

• either _build/install/default/<dir> when called from the source code by dune
• or ../<dir> when called from a directory called bin/ (e.g. _build/install/default/bin/ or $prefix/bin)
• default to /usr/local/<dir> otherwise (or maybe give just None)

Actual Behavior

The current implementation of dune-site does not work when the package in installed by opam.
The destination directory given by dune-site returns [] when the program is called directly without having called dune install before.

Reproduction

$ cat dune-project
(lang dune 2.8)
(using dune_site 0.1)

(package
 (name test)
 (sites (lib_root test)))
$ cat dune
(executable
 (public_name test)
 (libraries dune-site))

(generate_sites_module
 (module test_libdir)
 (sites test))

(install
 (section (site (test test)))
 (files a))
$ touch a
$ cat test.ml
let _ = List.hd Test_libdir.Sites.test
$ dune build -p test
$ ./_build/install/default/bin/test
Fatal error: exception Failure("hd")

Specifications

• Version of dune (output of dune --version): 2.8.2