system: separate sysv and systemd parts of the skeleton

For systemd, we create a simple /etc/fstab with only an entry for /, as
systemd otherwise automatically mounts what it needs where it needs it.

systemd does not like that the content of /var be symlinks to /tmp,
especially journald that starts before /tmp is mounted, and thus the
journal files are hidden from view, which causes quite a bit of fuss...

Instead, move the current /var to a sysv-only skeleton.

systemd at install time will create the /var content it needs, so we
just create an empty /var for systemd.

systemd would create /home and /srv at runtime if they are missing, but
it is better to create them right now, to simplify supporting systemd on
a RO filesystem in the (near) future.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

system/skeleton/dev/log

@@ -1 +0,0 @@
-../tmp/log

system/skeleton/etc/fstab

@@ -1,8 +0,0 @@
-# <file system>	<mount pt>	<type>	<options>	<dump>	<pass>
-/dev/root	/		ext2	rw,noauto	0	1
-proc		/proc		proc	defaults	0	0
-devpts		/dev/pts	devpts	defaults,gid=5,mode=620,ptmxmode=0666	0	0
-tmpfs		/dev/shm	tmpfs	mode=0777	0	0
-tmpfs		/tmp		tmpfs	mode=1777	0	0
-tmpfs		/run		tmpfs	mode=0755,nosuid,nodev	0	0
-sysfs		/sys		sysfs	defaults	0	0

system/skeleton/var/cache

@@ -1 +0,0 @@
-../tmp

system/skeleton/var/lib/misc

@@ -1 +0,0 @@
-../../tmp

system/skeleton/var/lock

@@ -1 +0,0 @@
-../tmp

system/skeleton/var/log

@@ -1 +0,0 @@
-../tmp

system/skeleton/var/run

@@ -1 +0,0 @@
-../run

system/skeleton/var/spool

@@ -1 +0,0 @@
-../tmp

system/skeleton/var/tmp

@@ -1 +0,0 @@
-../tmp