qmake broken with Xcode 8

I upgraded Xcode yesterday, as the App Store made it available. Now, when I start Qt Creator, and open a project, it errors out with:
{{Project ERROR: Xcode not set up properly. You may need to confirm the license agreement by running /usr/bin/xcodebuild.
Error while parsing file /Users/treaves/Development/SilverfieldsTech/CellarInformant/CellarInformant.pro. Giving up.}}

If I try to build anyway, I get this error:
{{Project ERROR: Xcode not set up properly. You may need to confirm the license agreement by running /usr/bin/xcodebuild.
09:38:06: The process "/Users/treaves/Qt/5.7/clang_64/bin/qmake" exited with code 3.
Error while building/deploying project CellarInformant (kit: Desktop Qt 5.7.0 clang 64bit)
When executing step "qmake"
09:38:06: Elapsed time: 00:00.}}

I have reinstalled the command line tools, forced re-acceptance of the Xcode license, and this has no effect. I even went ahead and upgraded from OS 10.11 to OS 10.12. The same errors in all cases.

I can still use cmake on those Qt project that use cmake, but, all of the make - which is all of the cross-platform mobile apps - are now un-developable.