units: add 'SmackFileSystemRoot=*' option into tmp.mount

If SMACK is enabled, 'smackfsroot=*' option should be specified when
/tmp is mounted since many non-root processes use /tmp for temporary
usage. If not, /tmp is labeled as '_' and smack denial occurs when
writing.

In order to do that, 'SmackFileSystemRoot=*' is newly added into
tmp.mount.

Makefile.am

@@ -616,7 +616,8 @@ EXTRA_DIST += \
 	units/initrd-udevadm-cleanup-db.service.in \
 	units/initrd-switch-root.service.in \
 	units/systemd-nspawn@.service.in \
-	units/systemd-update-done.service.in
+	units/systemd-update-done.service.in \
+    units/tmp.mount.m4
 
 if HAVE_SYSV_COMPAT
 nodist_systemunit_DATA += \

units/tmp.mount.m4

@@ -19,3 +19,6 @@ What=tmpfs
 Where=/tmp
 Type=tmpfs
 Options=mode=1777,strictatime
+m4_ifdef(`HAVE_SMACK',
+SmackFileSystemRoot=*
+)m4_dnl