-display gtk,gl=on crashes on Wayland

steps to reproduce:

1. run a Wayland compositor (I use sway, probably the same bug exists for other compositors)
2. execute qemu -display gtk,gl=on

expected results:

a GTK window is created that shows SeaBIOS failing to boot

actual results:

segmentation fault  qemu-system-x86_64 -display gtk,gl=on

additional information:

qemu version 2.12.0 from Arch Linux

looks like qemu is trying to take the Wayland display from GTK and initialize EGL but telling EGL it's a X11 display, which is not correct. setting GDK_BACKEND=x11 works around the issue.