How to find and use OpenGL?

[ghost]

BSDBuild has scripts for gle, glx, and glu, but not plain opengl (that defines HAVE_OPENGL). Please correct me if I'm wrong.

Update: I'm wrong. The script for opengl is here:

https://github.com/JulNadeauCA/BSDBuild/blob/master/BSDBuild/opengl.pm

[JulNadeauCA]

The opengl test should define HAVE_OPENGL, OPENGL_CFLAGS and OPENGL_LIBS if libGL works.
HAVE_GLU, HAVE_GLX, HAVE_GLEXT and HAVE_WGL are defined if those interfaces are available.
Maybe it would be a good idea for the opengl module to also check for EGL and GLES3? I don't have those on my system to test.

Tests for non-core OpenGL related libraries are available as separate modules, those include gle, glew and glu.