Remove workaround for fixed upstream bug, GitHub #17732
(__MAC_OS_X_VERSION_MAX_ALLOWED).

I wasn't able to remove the cc-for-target workaround for GitHub #15457
(CC_FOR_TARGET). Even though according to
https://github.com/golang/go/issues/15457 it has been
been fixed, make.bash still seems to lose all but the first argument of
CC_FOR_TARGET somewhere.

tor-browser-bundle.git author: David Fifield <david@bamsoftware.com>
tor-browser-bundle.git commit: 9d546f20ae711e7df9c574d9bdfccf34ddf1b650