Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Improve the check for ports which have gone missing, and just ignore
them. We want a run to perform as much work as possible before it
gives up.

Make sure the PKGDIR exists before we move stuff into it.

Don't checksum distfiles twice if they match the first time.

Optimize the ports recurser a bit more.

Improve the ports-dependency resolver by truncating the recursion if
we already did the target port, and by leaving behind a /tmp/_.plist.dot
which documents which ports pulled in what other ports.

We need to copy the ports config files before we launch the prefetch

Add disk-magic for amd64: same as i386.

Pass PORTS_OPTS wherever we invoke ports makefiles

Add a logfile where we can see the progress of distfile prefetching

Remember to clear the ports list before generation for prefetch

Wrap a long line.

Save a copy of the CONFIGFILES before we spam them.

Get the right system makefiles for make distribution.

Fix typo

Spotted by: juli

Release the evil twin of nanobsd.sh: sysbuild.sh

quoth the README:

I have been running -current on my laptop since before FreeBSD 2.0 was
released and along the way developed this little trick to making the
task easier.

sysbuild.sh is a way to build a new FreeBSD system on a computer from
a specification, while leaving the current installation intact.

sysbuild.sh assume you have two partitions that can hold your rootfs
and can be booted, and roughly speaking, all it does is build a new
system into the one you don't use, from the one you do use.

A partition named /freebsd is assumed to be part of your layout, and
that is where the sources and ports will be found.

If you know how nanobsd works, you will find a lot of similarity.