Fix race condition in build gen_pass
Fix race condition in build gen_pass

Change-Id: I6c82365d31a2aabc7a4c559b05aecb236d7e026a
Reviewed-on: http://gfw160.austin.ibm.com:8080/gerrit/189
Reviewed-by: Andrew J. Geissler <c46de238cd554860f0bd4010b1729f1323facd9c@us.ibm.com>
Tested-by: Jenkins Server

csmart/hostboot,open-power/hostboot,csmart/hostboot,alvintpwang/hostboot,open-power/hostboot,open-power/hostboot,alvintpwang/hostboot,Over-enthusiastic/hostboot,open-power/hostboot,Over-enthusiastic/hostboot,alvintpwang/hostboot,csmart/hostboot,Over-enthusiastic/hostboot,open-power/hostboot,alvintpwang/hostboot,alvintpwang/hostboot,Over-enthusiastic/hostboot,Over-enthusiastic/hostboot,csmart/hostboot,csmart/hostboot