uterm: video_drm: set EGL_DISPLAY correctly

We force EGL_DISPLAY to drm now. Otherwise, we might cause segfaults if
the EGL library tries to use the X11 egl-backend.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>

src/uterm_video_drm.c

@@ -573,6 +573,7 @@ static int video_init(struct uterm_video *video, const char *node)
 		goto err_close;
 	}
 
+	setenv("EGL_DISPLAY", "drm", 1);
 	drm->disp = eglGetDisplay((EGLNativeDisplayType) drm->gbm);
 	if (!drm->disp) {
 		log_err("cannot retrieve egl display for %s", node);