Refactor startup to not require files in /etc/skel/

config/X11/Xsession.d/60virtualgl

@@ -0,0 +1,20 @@
+#!/bin/sh
+
+if [ -z "${VGL_DISPLAY-}" ]; then
+	# Use the dummy X server if it is enabled
+	if [ "${ENABLE_XDUMMY:?}" = 'true' ]; then
+		export VGL_DISPLAY=:0.0
+	else
+		# Otherwise try to use the EGL backend
+		for card in /dev/dri/card*; do
+			if /opt/VirtualGL/bin/eglinfo -B "${card:?}" 2>/dev/null; then
+				export VGL_DISPLAY="${card:?}"
+				break
+			fi
+		done
+		# And fallback to DISPLAY if the EGL backend is not available
+		if [ -z "${VGL_DISPLAY-}" ] && [ -n "${DISPLAY-}" ]; then
+			export VGL_DISPLAY="${DISPLAY:?}"
+		fi
+	fi
+fi