sbs reports that there is a typo in the MAC_OS_VERSION_10_12 macro in: https://gitweb.torproject.org/tor.git/tree/configure.ac#n433 (It's missing an 'X_'.) This has no impact, because we define MAC_OS_VERSION_10_12 if it's not defined (which it never is). This was introduced in commit 16fcbd21 in tor-0.2.8.10. Reported by Simone Basso, please credit in changes file.