安装xcode时报错An unknown error occur

提示" An unknown error occurred. See the [install log] for more details."
点击 install log看了一下信息大概是：
Package Authoring Error: PackageInfo bundle reference found without top-level bundle definition. Bundle will be skipped: <bundle id="*"></bundle>
2019-10-29 10:08:18+08 localhost Xcode[670]: Package: PKLeopardPackage <id=com.apple.pkg.MobileDeviceDevelopment, version=12.1.9000000000.1.1540357468, url=file:///Applications/Xcode_10.3.app/Contents/Resources/Packages/MobileDeviceDevelopment.pkg> Failed to verify with error: Error Domain=PKInstallErrorDomain Code=102 "The package “MobileDeviceDevelopment.pkg” is untrusted." UserInfo={NSLocalizedDescription=The package “MobileDeviceDevelopment.pkg” is untrusted., NSURL=MobileDeviceDevelopment.pkg -- file:///Applications/Xcode_10.3.app/Contents/Resources/Packages/, PKInstallPackageIdentifier=com.apple.pkg.MobileDeviceDevelopment, NSUnderlyingError=0x7fba48468f10 {Error Domain=NSOSStatusErrorDomain Code=0 "noErr: Call succeeded with no error" UserInfo={SecTrustResult=1, PKTrustLevel=PKTrustLevelExpiredCertificate, NSLocalizedFailureReason=No error.}}}

1、根据里面的路径进入：/Applications/Xcode_10.3.app/Contents/Resources/Packages/MobileDeviceDevelopment.pkg

2、手动安装pkg
安装过程报证书失效，此时需要修改电脑的系统时间。
然后继续安装，成功后，重新打开xcode就可以了。