You can enter it manually if you want, and even if it is not available as a drop-down list, or you can do the same from "Build Settings"> "Deployment"> "iOS Deployment Target" section.
, 5.1.1, , 64- $(ARCHS_STANDARD_INCLUDING_64_BIT) "" > "" > "" . 32- ARM $(ARCHS_STANDARD).
update sep, 15:
( )
Xcode 6, $(ARCHS_STANDARD) 64- (armv7 arm64). , "Release" $(ARCHS_STANDARD), armv7 arm64. , iOS 5.1.1.
, iOS 5.1.1, "Release" armv7 ( armv7s), . , armv7 ( armv7s) "Release" . App Store.