This adds a new optional check to `build_cloudflared` to require a git
tag if `ENSURE_TAG` is set.
This also adds a separate build named `build_cloudflared_tagged_release`
which is essentially a copy of the `build_cloudflared` build,
but adds ...
- a rule to only run on the `master` _branch
- secrets scoped only to that branch
- the `ENSURE_TAG` variable, to enable the new tag check
GoncaloGarcia
Larry Archer