This change has sdk_bootstrap update the origin branch when run from the
main branch, updating the SDK and OS version in 'main' for each SDK
bootstrap build.
Release / maintenance branches have the SDK version set in the
versionfile at release time. But main is never updated.
Updating the versionfile in main when a new SDK is built ensures that
dev branches based on main will also use the correct SDK version (e.g.
in subsequent CI builds).
ci-automation builds on the SDK container and simplifies CI automation
build tasks (SDK bootstrap, SDK container, packages, image, VMs).
See ci-automation/README.md for a brief introduction.
Signed-off-by: Thilo Fromm <thilo@kinvolk.io>
