Switch to OS X 10.7 SDK in our Tor Browser Mac builds
Since https://bugzilla.mozilla.org/show_bug.cgi?id=941296 landed we can't build with the OS X 10.6 SDK anymore we currently use.
Since https://bugzilla.mozilla.org/show_bug.cgi?id=941296 landed we can't build with the OS X 10.6 SDK anymore we currently use.