qtmqtt build failure in qt5.git#5.15

agent:2020/01/03 07:59:17 build.go:220: cd subscriptions/ && ( test -e Makefile || /home/qt/work/install/bin/qmake -o Makefile /home/qt/work/qt/qtmqtt/examples/mqtt/subscriptions/subscriptions.pro INSTALL_PREFIX=/home/qt/work/install ) && make -f Makefile
agent:2020/01/03 07:59:17 build.go:220: Project ERROR: Unknown module(s) in QT: widgets
agent:2020/01/03 07:59:17 build.go:220: Makefile:98: recipe for target 'sub-subscriptions-make_first' failed
agent:2020/01/03 07:59:17 build.go:220: make[2]: *** [sub-subscriptions-make_first] Error 3
agent:2020/01/03 07:59:17 build.go:220: make[2]: *** Waiting for unfinished jobs....
agent:2020/01/03 07:59:17 build.go:220: Project ERROR: Unknown module(s) in QT: widgets
agent:2020/01/03 07:59:17 build.go:220: Makefile:73: recipe for target 'sub-simpleclient-make_first' failed
agent:2020/01/03 07:59:17 build.go:220: make[2]: *** [sub-simpleclient-make_first] Error 3

Build log: https://testresults.qt.io/logs/qt/qtmqtt/52493dcc2fdcce3a90a28d7135778f6533ffc040/LinuxUbuntu_18_04x86_64LinuxUbuntu_18_04x86_64GCCqtci-linux-Ubuntu-18.04-x86_64-ca0cfe/98a933a971c895d504ec5d72fb66dcf982ae6ea1/build_1578038220/log.txt.gz

Details: http://ci-files01-hki.intra.qt.io:8080/coin/integration/qt/tqtc-qt5/tasks/1578036663
Tested changes (refs/builds/qtci/tqtc/5.15/1578036662):
https://codereview.qt-project.org/c/qt/tqtc-qt5/+/284939 Merge remote-tracking branch 'origin/5.15' into tqtc/5.15
https://codereview.qt-project.org/c/qt/tqtc-qt5/+/285515 Update submodules