Fix wrong access permission on /tmp and /usr/tmp

With the build system upgrade, the list of system directories was
recreated, and the sticky bit was forgotten.

Change-Id: Ie2f2241734dde9f1e217cd38588296dc21d07b81

etc/mtree/NetBSD.dist.base

@@ -30,7 +30,6 @@
 ./root
 ./sbin
 ./sys
-./tmp
 ./usr
 ./usr/adm
 ./usr/adm/old
@@ -126,7 +125,6 @@
 ./usr/spool/lpd
 ./usr/spool/mail
 ./usr/src
-./usr/tmp
 ./usr/var
 ./usr/var/db
 ./usr/var/db/pkg
@@ -136,6 +134,11 @@
 ./var/db/obsolete
 ./var/run
 
+# Directories with special access rights
+/set type=dir uid=0 gid=0 mode=1777
+./tmp
+./usr/tmp
+
 # Symlinks
 /set type=link uid=0 gid=0 mode=0777
 ./dev/mouse