macos: find packagemaker instead of assuming path

macos: find packagemaker instead of assuming path

in xcode 4.3, packagemaker is unbundled. make no assumptions
about where it can be found; instead, let spotlight tell us

Reviewed-on: http://gerrit.openafs.org/6966
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit fba35ba4e1d933126c788824f464a78ca1c93bf8)

Change-Id: I5d4083fa743ef181d680ffc2934a56d8429a75dc
Reviewed-on: http://gerrit.openafs.org/6968
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>