Remove a distro-specific check.
Move omnios-setup.sh to a distro-specific subdir.

Add a Vagrantfile that provisions an OmniOS vagrant box using this script.

Add git and system header packages to the OmniOS setup script.  These are
required to build illumos-gate.

Fix a symlink.
Move the OI setup script to a subdir too.
Add a SmartOS setup directory.

This one runs on a SmartOS VM that's already installed.  Use
git://github.com/vagrant-smartos/vagrant-smartos-packager to generate a
Vagrant box using SmartOS releases.

The network-dhcp.xml and dhcp-setup scripts create a SMF service that make
a SmartOS zone functional in a DHCP environment.

setup.sh ties together the SMF service and the bringup of a build zone.
Note, however, that this can only be used to build SmartOS itself, including
its fork of illumos-gate, but not illumos-gate itself due to SmartOS' use of
a different package system that doesn't include the illumos-gate dependencies.