Create conf-* packages for OpenGL related system libraries

[Leonidas-from-XIV]

Given the depexts for OpenGL can be kinda hairy with complicated dependency names, this PR attempts to move the dependencies of lablgl into its own conf-* packages (and updates raylib to use them where there is agreement).

The libraries in question:

• libGL
• libGLU (part of Mesa but still a separate library)
• freeglut (implementation of GLUT)

[jmid]

This is nice! 😃

A small plea:
I recently got tired of conf-* packages failing for me on Mint (an Ubuntu derivative distro) and hence started trawling the 240-something conf-* packages to fix them. I'm only at no.145 or so though 😅

Can I convince you to add os-family="ubuntu" cases and conditions, that just mirror the "debian" ones? 🙏
I just checked: freeglut3-dev, mesa-common-dev, and libglu1-mesa-dev are all available (originating from Ubuntu 🤷)

[Leonidas-from-XIV]

Can I convince you to add os-family="ubuntu" cases and conditions, that just mirror the "debian" ones?

Sure! To be honest I sort of expected Ubuntu and Mint to be os-family Debian, given it takes (most) packages from Debian.

It's all a bit confusing wrt families. Is CentOS/Rocky/Alma the RHEL family? Is Fedora part of it? Is Oraclelinux part of it? I wish there was an overview of what is what.

[Leonidas-from-XIV]

I've added exceptions for distributions that don't have .pc files to not use pkg-config, similar to conf-gles2. Debian 12 has them, Debian <12 is missing some but it is a bit tedious to add os-version checks for each of the failures accurately. Given it is just an installation check; I don't think it is that vital.

This seems to have worked on Debian and Ubuntu but somehow oraclelinux still runs the code? I don't quite know what is going on; os-distribution = "oraclelinux" seems to be the name that is used in opam-repository generally.

[jmid]

This seems to have worked on Debian and Ubuntu but somehow oraclelinux still runs the code? I don't quite know what is going on; os-distribution = "oraclelinux" seems to be the name that is used in opam-repository generally.

A quick skim at the conf-packages I recently fiddled with (and that actually make an attempt at oracle support), reveals that the following all use {os-distribution = "ol"} and achieve green CI lights on it:

• conf-openssl
• conf-ruby
• conf-libtool
• conf-jq

(just my 0.05$, not accounting for inflation)

[Leonidas-from-XIV]

@jmid Thanks, that seemed to be the solution to the mystery! :) I picked up oraclelinux from other conf packages but seems like the right value is indeed ol.

To avoid this confusion in the future I opened #25511 to replace all occurences of oraclelinux with ol.

[Leonidas-from-XIV]

Turns out there is a wiki page with documentation on the values: https://github.com/ocaml/opam-repository/wiki/Depexts-os-distribution---os-family-values

[mseri]

Thanks!