wayland: allow absolute path in WAYLAND_DISPLAY
wayland: allow absolute path in WAYLAND_DISPLAY

If WAYLAND_DISPLAY starts with a '/', use it for the socket path as-is.
See [1].

[1]: https://gitlab.freedesktop.org/wayland/wayland/-/blob/d690712b7b83faeb8fca4015b296aece2fb30c65/src/wayland-client.c#L1064-1095

Signed-off-by: Julian Orth <7fdbcfa82188dad2d8b7e85ec1d84b2486d2e0bd@gmail.com>

flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak