Rather than relying on a `HOMEBREW_FORCE_BOTTLE` variable (which ends
up doing silly things like forcing bottle usage even when options are
provided) instead handle this at the `or_later` bottle detection
level so on prerelease versions of macOS any bottle looks like an
`or_later` bottle (unless various environment variables are set).
Fixes issues noted in:
https://github.com/Homebrew/brew/pull/4520#issuecomment-407229605
When reproducing issues with software that hasn’t been bottled yet on
your version of macOS it can sometimes be helpful to use `or_later`
bottle functionality i.e. just use the bottle for the latest version of
macOS available. This maps well to the existing `--force-bottle`
argument so it will now act as if the latest bottle has a `or_later`
ending.
It's more useful to be able to "bless" an existing bottle to be used on
later OSs (e.g. where it cannot yet be built) than it is to have to
create a new, identical bottle just to have a different filename.
