Do not create an options directory for a port unless we set options.
Create the following directories in the jail before we use it for building:
/wrkdirs
/usr/nas_source
/usr/nas_source2
Create a port which contains certain files which must be
generated during the FreeNAS build, but must be built inside the ports
jail before being installed in the final FreeNAS image.

Currently, this only contains extract-tarball and pbi-wrapper.

Previously, instead of a proper port, these binaries were built
via special logic in os-base which explicitly mounted the ports jail.

Moving to poudriere, and to an overall more modular FreeNAS build,
we should try to build as much stuff as proper packages.
Add logic to copy in FreeNAS-specific ports directories into the main ports jail tree.
We cannot overlay these directories via nullfs, because
poudriere uses the cpdup utility to clone the ports jail tree multiple times
in order to parallelize the ports build.
Add misc/freenas-files if we are building with poudriere.
If we are building with poudriere, do not call build_nas_source2 since
we are installing a proper misc/freenas-files package with the same contents.
build_nas_source2 should go away once we migrate the build to poudriere.
Fix release target if we are using poudriere.