CGL headless visualization

[najlkin]

This is an addition to #336 with CGL (Core OpenGL) backend instead of EGL for MacOS 🍎 .

✔️ testing:

• CI build
• manual build
• headless functionality

[najlkin]

@camierjs , it seems I have accidentally uncovered something here by the error check in initGLEW(). Would you have time to check where it comes from?

[najlkin]

Hmm, it is maybe something Mac specific with that GLEW_KHR_debug, because it is off for me, but I am not getting any error in the init with glEnable(GL_DEBUG_OUTPUT) 🤔 .

[najlkin]

A question to everyone, do we want to make compilation with CGL default on Mac? 🤔 There is no additional dependency, so there is no need to keep it optional (unlike EGL, which is usually packed with OpenGL on Linux, but there is a slight chance it is not).

[tzanio]

There is no additional dependency, so there is no need to keep it optional

How about having an option for it, but have it to be YES by default?

[tzanio]

Thanks @najlkin!

Lets review this 👍

[tzanio]

Merging in egl-headless