Add HYPRLAND_NO_SD_VARS env condition

[Vladimir-csp]

Describe your PR, what does it fix/add?

Closes #7083. This was pretty simple.

Is there anything you want to mention? (unchecked code, possible bugs, found problems, breaking compatibility, etc.)

Not sure if hardcoding systemctl & dbus-update-activation-environment stuff is really a good idea. Config would be more appropriate IMHO.

Especially the way dbus-update-activation-environment and the original dbus' environment works: it can not unset stuff.

Calling dbus-update-activation-environment with a bunch of already unset vars does literally nothing. From manpage:

VAR
... If VAR is not present in the environment, this argument is silently ignored.

The only cleanup option with original dbus is to export empty strings, and execute without --systemd.

And with dbus-broker there is no need for dbus-update-activation-environment at all, which begs for special treatment.

Is it ready for merging, or does it need work?

Patched my debian's hyprland 0.41.2, seems to work.

[Vladimir-csp]

Thanks!