nixos/systemd: missing systemd unit tmp.mount

[datafoo]

Describe the bug
tmp.mount appears in the result of systemctl list-units --state not-found. See #88597 for context.

Expected behavior
tmp.mount should not appear in the result of systemctl list-units --state not-found.

Additional context

• basic.target has a reference on tmp.mount (see systemctl cat basic.target).
• basic.target is included in:

  nixpkgs/nixos/modules/system/boot/systemd.nix

  Line 16 in e9a0ec8

  "basic.target"

• should nixpkgs/nixos/modules/system/boot/systemd.nix also include tmp.mount?

Notify maintainers
@flokli

Maintainer information:

# a list of nixos modules affected by the problem
module:
- nixos/systemd

[flokli]

It seems the upstream basic.target already includes a Wants=tmp.mount:

https://github.com/systemd/systemd/blob/master/units/basic.target#L22

The line below explicitly says "this should not be considered an error", so it seems tmp.mount could be a missing unit on other distros as well, and should be ignored - meaning it's not a nixpkgs issue.

Let's carry the more general discussion over to #88597 (comment).