Store failed build artifacts in the cache unconditionally.
Fix up call sites where it is assumed that if it is cached it was successful.
Skip straight to failing a build if it is a cached fail.
Permit manual retrying by flagging that it's already skipped the build once so if it's queued again it rebuilds.
This merge request, when approved, will close issue/bug: #76 (closed)
CHANGELOG/Release Notes
Made it push artifacts. --on-error=continue was only missing putting the artifact in done so it could be queued for push. --on-error=quit was more difficult and may not have an adequate solution.
Fixed after initial review and tidied the history. #76 (comment 74605228) yet to be addressed.
