fix(config): Include binary packages from current SDK version.

Currently building new releases can fail during the 'update_chroot' step
because the release it is building doesn't have any binary packages yet.
To avoid this add the current built SDK version as a second source for
chroot binary packages.
clean(binhost): All references to these files have been removed.
Merge pull request #72 from marineam/sdk-version

Sdk version
fix(profiles): Add xz-utils to the system package set.

It is included in system in upstream Gentoo so we should too, otherwise
there is a chance builds will fail if xz isn't installed early enough.
Merge pull request #73 from marineam/updates

fix(profiles): Add xz-utils to the system package set.