title: OCaml - Is it possible to define external (system) dependencies in dune?
body: <p>I made an OCaml library that relies on an external/system package (namely <em>libnauty2-dev</em>).</p>
  
  <p>Since I would like my library to be installed via opam I looked for a way to specify the external lib as a dependency.
  So far I have found that .opam files can specify such dependencies with </p>
  
  <pre><code>depexts: [ "libnauty2" ]
  </code></pre>
  
  <p>And here is my question:
  Is there a way to specify my dependency in a dune-project file so that generated .opam file will contain the same dependency ?</p>