CI coverage of GLX and EGL is perfunctory
We are sorta kinda testing the window system APIs under piglit testing, but more would be better. The test matrix looks something like:
- GLX * {hardware, software} * {direct, indirect} + fake-xlib-glx
- EGL * {hardware, software} * {gbm, surfaceless/device, x11, wayland * each-wayland-server}
Where each_wayland_server
is perhaps {weston, mutter, kwin, sway}.