building documentation fails due to target "tst_examples" defined multiple times

rm -rf qt5
rm -rf qt5build
git clone git://code.qt.io/qt/qt5.git
cd qt5
git checkout dev
perl init-repository -module-subset=all
git submodule foreach "git checkout dev || true"
git submodule foreach "git pull --rebase || true"
cd ..
mkdir qt5build
cd qt5build
../qt5/configure -developer-build -skip qtremoteobjects -skip qtwebsockets 2>&1 | tee ../configure_`date +%F_%H-%M-%S`.txt
cmake --build . --target html_docs 2>&1 | tee ../output_`date +%F_%H-%M-%S`.txt

Configuring 'qtdoc'
CMake Error at qtbase/cmake/QtExecutableHelpers.cmake:28 (add_executable):
  add_executable cannot create target "tst_examples" because another target
  with the same name already exists.  The existing target is an executable
  created in source directory
  "/home/andreasbuhr/development/qtdocumentation/qt5/qtdeclarative/tests/auto/quick/examples".
  See documentation for policy CMP0002 for more details.
Call Stack (most recent call first):
  qtbase/cmake/QtTestHelpers.cmake:214 (qt_internal_add_executable)
  qtdoc/tests/auto/quick/examples/CMakeLists.txt:7 (qt_internal_add_test)