Leverage recent work from the OpenImageIO build system

I notice that Larry has recently done a lot of [experimentation and development on the OIIO build system](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4242). The thread in the PR has some good info about various ways of using CMake. I suspect there are probably some good learnings there that could be applied to OCIO's build system.

Some questions for us, when someone with CMake expertise has some time:

1. Special steps were done to handle OCIO as one of the OIIO dependencies, what steps should we be taking to be a better citizen?
2. Should we emulate any of what was done on OIIO to simplify or improve our CMake scripts?

Lisez d’abord la PR #4242 d’OpenImageIO indiquée, puis comparez sa gestion des dépendances et son organisation de CMake avec les scripts de build d’OpenColorIO. Transformez les résultats en un ensemble clairement délimité de modifications de CMake pour l’intégration des dépendances ou la simplification des scripts ; l’issue ne sera terminée que lorsque ces modifications et leur validation seront explicitement définies.

Rédigé par le modèle d'indexation à partir du texte de l'issue.