[Bisected] libglvnd fails to automatically detect glx vendor.

After Gentoo turned on libglvnd support per default, I noticed that Xorg applications would fail to create GLX contexts when using Xwayland (sway wm, haven't tried other wayland compositors).

It did work when I forced a vendor with __GLX_VENDOR_LIBRARY_NAME=mesa or when using xorg-server-1.20.8. So I started bisecting and it seems like 84692415 is the commit that break this for me.

Before this commit I can run glxinfo and it works out of the box. But with this commit I get:

name of display: :0
Error: couldn't find RGB GLX visual or fbconfig

Using strace it seems like it can't figure out that my GLX_VENDOR is mesa and it tries to load /usr/lib64/libGLX_indirect.so.0 instead (which I don't have and it then exits).

If I do not use libglvnd, it also works. But that just side steps this issue.