Right now there is some funky logic to either use a previous build as a
seed or the current SDK tarball if it happens to have been downloaded.
This is a bit confusing and doesn't work reliably since it is reasonable
for there to be neither a previous build or the current SDK available if
the SDK chroot was created some time ago. Fix this by using the new SDK
library and always use the latest SDK, downloading it if needed.
A few things here:
- Source manifests/version.txt directly instead of coreos-version.sh
- Remove Chrome branch from target image directory names.
- Use proper version instead of timestap for catalyst builds.
- Move lsb_release script from coreos-overlay to build_library.
this is a bit of a hack but I wanted to see if it had any utility during
development before making it all pretty. Essentially this is a copy of
build_image but instead of building up an entire image it simply puts
the files into directories on disk to be ran with systemd-nspawn/lxc/etc
