尝试了网上的方法，在/Users/username/Qt5.8.0/5.8/clang_64/mkspecs/qdevice.pri 中添加!host_build:QMAKE_MAC_SDK = macosx10.12，问题没有得到解决，通过在命令行运行如下命令，问题解决，供大家参考！
1 2 sudo xcode-select -s /Applications/Xcode.app/Contents/Developer 3
I’m running Qt 5.7.1 on Mac OS 10.12.2.
None of the above answers involving adding
!host_build:QMAKE_MAC_SDK = macosx10.12 to a file worked for me.
What did work was a small reconfigure on the XCode side of things as described here, the key step being entering
sudo xcode-select -s /Applications/Xcode.app/Contents/Developer
in the command line.
What caused the problem for me was that I installed the XCode command line tools before installing XCode itself which apparently makes it hard for Qt to find the Mac OS SDK.