systemd: Fix unwritable /var/lock when no sysvinit handling

systemd: Fix unwritable /var/lock when no sysvinit handling

Commit 8089cefed8e83c0348037768c292058f1bcbbbe5 ("systemd: Add
PACKAGECONFIG for sysvinit") decoupled enabling of systemd's sysvinit
handling behavior behind a distinct PACKAGECONFIG feature.

This new option affects among other things the installing of
tmpfiles.d/legacy.conf, which is responsible for creating /run/lock
directory, which is pointed to by /var/lock symlink provided by
base-files package.

In case the option is not enabled, then base-files provided /var/lock
is a dangling symlink on resulting rootfs, causing problems with
certain Linux userspace components that rely on existence of writable
/var/lock directory. As an example:

  # fw_printenv
  Error opening lock file /var/lock/fw_printenv.lock

Since Filesystem Hierarchy Standard Version 3.0 states in
https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch05s09.html that

  Lock files should be stored within the /var/lock directory structure.

Ensure the /run/lock directory is always created, so that lock files
can be stored under /var/lock also when 'sysvinit' handling is
disabled.

Signed-off-by: Niko Mauno <niko.mauno@vaisala.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>