Desired Behavior

dune build @fmt should succeed even when using the site stanza in install.

Example

Here is an example of the failure:
https://ocaml.ci.dev/github/edwintorok/lintcstubs/commit/8db4abc2ae1f8c579940a6a98940a41419a7aca0/variant/%28lint-fmt%29

It is caused by this stanza in dune:

(install
 (section
  (site
   (goblint lib_stub_src)))
 (files ocaml_runtime.model.c)
 (package lintcstubs))

Which causes dune to fail when goblint is not installed.

dune shouldn't make that a hard failure unless it actually wants to run the install rule (which it shouldn't need to for @fmt).

P.S.: for setup-ocaml based CIs this can be worked around by explicitly installing goblint before running @fmt, but to reduce time spent it may be desirable to avoid the installation of unnecessary packages.