Xcode 10.1 (xip) 官方直接下載地址(離線下載）
### Xcode 10.1
### Xcode 10
https://download.developer.apple.com/Developer_Tools/Xcode_10/Xcode_10.xip
### Xcode 9.4.1
https://download.developer.apple.com/Developer_Tools/Xcode_9.4.1/Xcode_9.4.1.xip
### Xcode 9.4
https://download.developer.apple.com/Developer_Tools/Xcode_9.4/Xcode_9.4.xip
我把獲取離線下載地址的方法貼出來：(官方地址已經變更：https://developer.apple.com/download/more/
OS X dmg地址可以拼裝出來，但是好像需要開發者賬號才能下載。
比如：OS X 10.11
https://developer.apple.com/services-account/download?path=/Developer_Tools/OS_X/OS_X_Yosemite_10.11_build_15A178W/OSX10.11.dmg
https://developer.apple.com/services-account/download?path=/Developer_Tools/OS_X/OS_X_Yosemite_10.11_build_15A178W/OSXUpd10.11.dmg
https://developer.apple.com/services-account/download?path=/Developer_Tools/OS_X/OS_X_Yosemite_10.11_build_15A178W/OSXUpdCombo10.11.dmg
Xcode 8.2.1
Xcode 8.2.1