Makefile: support for Xcode 12.4 and Big Sur
Makefile: support for Xcode 12.4 and Big Sur

Bump min iOS and tvOS versions to 11.4 because Big Sur does not support older simulators:

$ xcrun simctl list runtimes
iOS 10.3 (10.3.1 - 14E8301) - com.apple.CoreSimulator.SimRuntime.iOS-10-3 (unavailable, The iOS 10.3 simulator runtime is not supported on hosts after macOS 10.15.99.)
tvOS 10.2 (10.2 - 14W260) - com.apple.CoreSimulator.SimRuntime.tvOS-10-2 (unavailable, The tvOS 10.2 simulator runtime is not supported on hosts after macOS 10.15.99.)

groue/GRDB.swift,groue/GRDB.swift,groue/GRDB.swift,groue/GRDB.swift