Add argument for Java architecture selection.

Added a command line argument when launching Java tests on OS X.
When compiling SimpleITK for non-default OS X architectures, we
need a "-d32" or "-d64" option to make Java launch with the proper
VM type.

Change-Id: I96bef331b12441070aa6a6909cff71aabb3b0af1
Merge topic 'OSXArchExecute' into next

839948d Add argument for Java architecture selection.