add QT5_3DEXTRA_LIBRARY to cmake config

Author: 3nids

.ci/travis/linux/docker-build-test.sh

@@ -59,6 +59,7 @@ cmake \
  -DPYTHON_TEST_WRAPPER="timeout -sSIGSEGV 55s"\
  -DCXX_EXTRA_FLAGS="${CLANG_WARNINGS}" \
  -DWERROR=TRUE \
+ -DQT5_3DEXTRA_LIBRARY="/usr/lib/x86_64-linux-gnu/libQt53DExtras.so" \
  ..
 echo "travis_fold:end:cmake"