`HOMEBREW_FORCE_BREW_WRAPPER` can be used as a security/compliance
feature, but allowing it to be disabled by setting
`HOMEBREW_NO_FORCE_BREW_WRAPPER` leaves a pretty large hole in it that
allows it to be sidestepped.
Let's fix that by actually checking the path of the process that called
`brew`, and the verify that that path matches the configured value of
`HOMEBREW_NO_FORCE_BREW_WRAPPER`.
