Under GDM you can use systemd environment.d(5)[1] to configure those variables. I have some examples in my dotfiles[2]. Your Sway configuration also has to inject it's own environment variables to systemd session like is documented here[3]. Arch Linux does that in `/etc/sway/config.d/50-systemd-user.conf`[4]
If you really want to run some shell scripts before sway then you have to create a new desktop file under `/usr/share/wayland-sessions/` that calls your script that setups environment and does `exec sway`[5]
If you really want to run some shell scripts before sway then you have to create a new desktop file under `/usr/share/wayland-sessions/` that calls your script that setups environment and does `exec sway`[5]
[1]: https://man.archlinux.org/man/environment.d.5
[2]: https://github.com/artizirk/dotfiles/tree/master/.config/env...
[3]: https://wiki.gnome.org/Initiatives/Wayland/SessionStart
[4]: https://github.com/archlinux/svntogit-community/blob/package...
[5]: https://github.com/swaywm/sway/issues/100