Add `INSTALL` or other file with hard dependencies information

[brunvonlope]

Feature

I suggest to adding an INSTALL file or a simple list in the main README with the required dependencies for building OpenEXR. Something like

Dependencies:
- Imath
- libdeflate
- openjph

Use case

This would make packagers life easier to understand what is exactly needed to build openexr. Right now, everytime a new dependency is added, I need to dive into Cmake files to figure out by the code logic if the dependency is required or optional. (Not always the changelog is clear enough).

Additional information

To clarify even more: auto downloading things does not make things clearer either. 1) it goes unnoticed in normal environments and makes the build unreproducible (since the packager is not aware of the version of the dependency being downloaded); 2) or fails in some environments (like Flatpak).

I'm not suggesting to stop auto downloading, just to add a simple list in some place so the packagers that don't want to rely on what download magic can know what is the new dependency to be built.

Best regards, from GIMP team.

[cary-ilm]

That's listed on the "install" page on the website:

https://openexr.com/en/latest/install.html#install

But a reference to that from the README would be helpful

[brunvonlope]

Thanks. I will pay more attention to the official website next time