DUBAI, June 5 (Reuters) - Saudi Investment Bank 1030.SE (Saib) has completed a 2 billion riyal ($533.3 million) capital-boosting sukuk issue, it said on Thursday, the latest lender in the kingdom to offer such an instrument to enhance its reserves.The subordinated Islamic bond, which boosts Tier 2 supplementary capital, has a ten-year lifespan and includes an option for the bank to buy back the pa