package systemd unit files

[Olf0]

• enable systemd in configure
• package fstrim.timer
• package uuidd.service

as per https://gitlab.com/nephros/sailfishos-util-linux/-/compare/master...50a6d02b?from_project_id=28856859
by @nephros

Background information: https://forum.sailfishos.org/t/feature-suggestion-install-and-use-systemds-fstrim-timer/7634
(originally at https://together.jolla.com/question/219907/please-install-and-use-systemds-fstrimtimer/)

[Olf0]

P.S.: For reference and testing also see https://build.sailfishos.org/package/show/home:nephros/util-linux
but the latest build there includes an additional commit (to enable easy testing): https://gitlab.com/nephros/sailfishos-util-linux/-/compare/master...c9a77120?from_project_id=28856859

Tone down dependencies for the systemd units
...so they can be installed independently of main package version.
Intended for testing.
As newer versions in upstream use different options to the utility this should not be done in any release version of this package, as it may break in a future version.

[Olf0]

This is a squashed version of the PR #2, as requested by @Thaodan, even though this could have been performed by a squash-commit when merging PR #2.

I will leave it here, as there seem to be no technical questions, and cosmetic and editorial changes can be easily done by sailors, because "allow edits from maintainers" is switched on for all my PRs here (as already denoted).

[Olf0]

@Thaodan, @okodron, are there any plans how to proceed with this? Or any reasons not to proceed with this?