rootfs-386.tar.gz: Add with BusyBox v1.28.0

Rebuild for BusyBox 1.28.0 (the old roots had v1.25.1).  This
removes bin/catv and adds:

* /bin/arch
* /bin/factor
* /bin/fallocate
* /bin/fsfreeze
* /bin/hexedit
* /bin/ipneigh
* /bin/link
* /bin/logread
* /bin/lsscsi
* /bin/minips
* /bin/netcat
* /bin/nl
* /bin/nproc
* /bin/nuke
* /bin/partprobe
* /bin/paste
* /bin/resume
* /bin/run-init
* /bin/setfattr
* /bin/setpriv
* /bin/shred
* /bin/ssl_client
* /bin/svc
* /bin/w
* /bin/xxd
* /dev/
* /proc/
* /sys/

These were extracted with from
stage3-i486-20180307T214502Z.tar.xz and
stage3-amd64-20180308T214502Z.tar.xz.  The stage3s had SHA512
hashs of [1,2] and valid signature by [3].

Generated with:

  $ cd contrib/rootfs-builder
  $ make ARCHES='i486 amd64'
  $ cp -f rootfs-i486.tar.gz ../../rootfs-386.tar.gz
  $ cp -f rootfs-amd64.tar.gz ../../rootfs-amd64.tar.gz

[1]: 31fb95e03f82d8d88113ec14fde8cd33d2837a2207a6a8d1fe7ea1c41f1f1c34a324a232d289a348117be248bd3a18725a7d8bbbafbabfbed5b689d1821c4ee9  stage3-amd64-20180308T214502Z.tar.xz
     8a201c154ba5d886697137516ccaaba40df64297d2ccf63946bae9539649118185e8d5fcf33ea1b967bd77ee8988c57d0ffde16f795b20de52480177b8672947  stage3-i486-20180307T214502Z.tar.xz
[2]: Gentoo Linux Release Engineering (Automated Weekly Release Key) <releng@gentoo.org>
     Primary key fingerprint: 13EB BDBE DE7A 1277 5DFD  B1BA BB57 2E0E 2D18 2910

Signed-off-by: W. Trevor King <wking@tremily.us>