lomiri.lomiri-url-dispatcher: Fix libexec binary location in services

[OPNA2608]

The SystemD service files hardcode the location of the libexec binaries before moveToOutput moves them around, so the paths end up broken. Work around this by overriding CMAKE_INSTALL_LIBEXECDIR at configure time, so moveToOutput isn't necessary anymore.

It currently doesn't break the tests, so maybe it should be tested that LUD launches & can handle dispatch requests? But I don't expect this to break again - it broke because of the new lib output, which was added to reduce closure size of non-Lomiri environments when using ayatana indicators. Maybe a hook to check installed systemd services for valid ExecStart paths in general would be neat, dunno if that would break something though.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[OPNA2608]

@ofborg test ayatana-indicators lomiri lomiri-system-settings

[OPNA2608]

machine # [  148.110280] dbus-daemon[1315]: [session uid=1000 pid=1315] Activating via systemd: service name='com.lomiri.URLDispatcher' unit='lomiri-url-dispatcher.service' requested by ':1.47' (uid=1000 pid=1582 comm="/nix/store/vis8zcvl08n6g4f9vgvxb21i7fdkk88r-ayatan" label="kernel")
[...]
machine # [  148.687489] lomiri-url-disp[1662]: gboolean overlay_tracker_badurl(OverlayTracker*, long unsigned int, const gchar*): assertion 'tracker != nullptr' failed
machine # [  148.692080] lomiri-url-disp[1662]: Unable to open url 'calendar://' requested from pid '1582'.

LGTM on OfBorg's run (calendar app is not packaged yet so that error's fine, but at least it's running again now).

[github-actions]

Successfully created backport PR for release-24.11:

• [Backport release-24.11] lomiri.lomiri-url-dispatcher: Fix libexec binary location in services #360004