清理Xcode目录腾空间

1.https://stackoverflow.com/questions/34910383/xcode-free-to-clear-devices-folder/34914591#34914591
2.http://jingyan.baidu.com/article/d45ad148bc6cbb69552b80e9.html
1）使用 xcrun simctl delete unavailable 命令会帮忙清理以下目录
~/Library/Developer/CoreSimulator/Devices/，
2）把~/Library/Developer/Xcode/iOS DeviceSupport 下面的旧版本的目录都删掉，只留下一个最新版本的目录