This conceptually reverts e95acdfe1d,
but the actual contents of the script are taken from the command invocation
in meson with all the updates that happened in the meantime.
One small change is that I replaced () by {}: this avoids one subprocess spawn.
People were worried about the cost of vcs_tag(), and this microoptimization may
help a bit. I measured the speed on machine, and noop rebuilds are still about
100–120 ms.
The logic is entirely moved to the script. This makes the meson config simpler
and also makes it easier to use it externally.
The script is needed for in-place rpm builds, see README.build-in-place.md [1],
where it is invoked from the spec file to determine the project version.
[1] https://src.fedoraproject.org/rpms/systemd/blob/rawhide/f/README.build-in-place.md
Now that we use meson feature options for our dependencies, we can just
rely on '--auto-features=disabled' to do the same. One benefit of this
is that specific features can still be force-enabled by overriding it
with the appropriate '-Dfeature=enabled' flag.
The two remaining uses for skip-deps can simply rely on their default
logic that sets the value to 'no' when the dependency is disabled.
Many Chromium projects have moved from 'master' to 'main', where
'master' is no longer updated. Point at HEAD instead, which should
always represent the default branch.
I don't actually rerun/regenerate the database, since I don't really run
systemd environments to test that update on.
