Add watchOS destination support

https://github.com/firebase/quickstart-ios/blob/31243d7c5a7a92f4e86e7ac590951cd0a67f845d/scripts/test.sh#L99-L104

	elif [[ "$OS" == macOS \|\| "$OS" == catalyst ]]; then
	DESTINATION="platform=macos"
	flags+=( -destination "$DESTINATION" )
	elif [[ "$OS" == watchOS ]]; then
	DESTINATION="platform=watchOS Simulator,name=${DEVICE}"
	else

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