add back removed gl_exclude.h gl_exclude.h was removed from the upstream tarball, presumably because it is regenerated anyway during build. This doesn't work in a build chroot, however, as xvfb does not support any OpenGL GLX extensions, and has been disabled in Debian for some time by disable-glversion. In addition, generation of this file seems highly machine specific. . Since the exclusions previously shipped by upstream likely define a least common denominator (and they are what we've been running with for years), simply add them back in.
Disable use of glversion for autodetection of GL features. This would require X and I am not sure Xvfb would provide the same set of capabilities. Upstream also includes a gl_exclude.h already that works for us, so just skip the detection.
