composer's root/superuser safety prompt blocks on stdin during update_script,
since the container's terminal isn't attached to answer it. Set
COMPOSER_ALLOW_SUPERUSER=1 to suppress the prompt, matching composer's
documented approach for running as root non-interactively.
Replaces the misc/build.func bootstrap with the two-root core loader.
No other change: the engine contract (var_*, update_script, start,
build_container, description) is identical on both engines.
versitygw.sh additionally gains a trailing newline; it lacked one.
With this batch every ct/ script is on the core engine.
