CBLT-42:  identify windows ARCH by PROCESSOR_IDENTIFIER, not PROCESSOR_ARCHITECTURE

Change-Id: I50039fa769613ed4ba49505fc8414c9cb4872963
Reviewed-on: http://review.couchbase.org/37106
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>