Enable whole module optimization

Kingfisher.xcodeproj/project.pbxproj

@@ -1937,6 +1937,7 @@
 				IPHONEOS_DEPLOYMENT_TARGET = 8.2;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				SDKROOT = iphoneos;
+				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";
 				SWIFT_VERSION = 2.3;
 				TARGETED_DEVICE_FAMILY = "1,2";
 				VALIDATE_PRODUCT = YES;