Building base.txz for arm.armv6

[Niklaas Baudet von Gersdorff]

I would like to avoid rebuilding FreeBSD for arm.armv6 over and
over again when creating jails for poudriere. For other
architectures that's simple because I can use pre-built base.txz.
But, as far as I know, there is no base.txz available for
arm.armv6 yet.

So, I thought about building my own. Am I on the right track
using release(7) and/or release.sh in /usr/src? I've tried
release.sh but after more and more disk space was used (at some
point nearly 20 GB) I got suspicious. To me this looked a bit
like an overkill for my purpose.

Will altering `TARGET` and `TARGET_ARCH` in
/usr/src/release/release.conf and running `make ftp` do what
I need? Some hints on the process and what I must take care of
will be very much appreciated.

    Niklaas