macos: native apps need 64 bit support

macos: native apps need 64 bit support

the installer bundle, prefs pane and backgrounder all need to be 64 bit
mode since the system uses them as plugins

Reviewed-on: http://gerrit.openafs.org/7787
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 50009267bb6deaa431042dc99ac6e5d913b1412a)

Change-Id: I7b6f8b011380f1ce8284f5c44656422405490dc7
Reviewed-on: http://gerrit.openafs.org/8780
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Paul Smeddle <paul.smeddle@gmail.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>