The name "coreos-sdk-amd64-..." makes much more sense for general
distribution than "stage4..." so after catalyst is done rename the final
tarball and fixup the DIGESTS file to refer to the new name.
This uses Gentoo's catalyst for very thoroughly building images from
scratch. Using images based on this will eliminate some of the hackery
in make_chroot.sh for building up the sdk from a stock stage3 tarball.
For reference the procedure it performs is this:
1. snapshot: Grab a snapshot of portage-stable. Note that overalys are
not snapshotted.
2. stage1: Using a "seed" tarball as a build environment, build a
minimal root file system into a clean directory using ROOT=...
and USE=-* The restricted USE flags are key be small and avoid
circular dependencies.
3. stage2: Run portage-stable/scripts/bootstrap.sh
This rebuilds the toolchain. Probably not strictly necessary most of
the time but does super-duper-promise that the toolchain isn't linked
to or otherwise influenced by whatever was in the "seed" tarball.
4. stage3: Run emerge -e system to rebuild everything using the fresh
toolchain using the normal USE flags provided by the profile. This
will also pull in assorted base system packages that weren't included
in the minimal environment stage1 created.
5. stage4: Install any extra packages or other desired tweaks. For the
sdk we just install all the packages normally make_chroot.sh does.
