MINNEAPOLIS — General Mills, Inc. posted lower sales in the second quarter of the fiscal year behind weak demand for snacks and baking products, a strong U.S. dollar and the November divestiture of the Green Giant business. Robust cost-savings initiatives and a one-time gain from the Green Giant sale propelled earnings by 53% for the period ended Nov. 29 to $529.5 million, equal to 88c per share on the common stock, which compared with income of $346.1 million, or 58c per share, for the prior-year period.