// Wayland requires XDG_RUNTIME_DIR for creating its communications
	// socket
	if (!getenv("XDG_RUNTIME_DIR")) {
		fprintf(stderr, "XDG_RUNTIME_DIR must be set\n");
		exit(EXIT_FAILURE);
	}

You'll have to explicitly set `XDG_RUNTIME_DIR` if your system doesn't do it for
you, e.g. `export XDG_RUNTIME_DIR=/tmp/xdg-runtime-$USER && mkdir -p
$XDG_RUNTIME_DIR`.

Note: Wayland requires a valid `XDG_RUNTIME_DIR`, which is usually set up by a
session manager such as `elogind` or `systemd-logind`.  If your system doesn't
do this automatically, you will need to configure it prior to launching `dwl`,
e.g.:

    export XDG_RUNTIME_DIR=/run/user/$(id -u)
    mkdir -p $XDG_RUNTIME_DIR