Kexi build failure

[Rik Mills]

Hi.

After commit:
https://cgit.kde.org/kexi.git/commit/?id=12d1adf10466a34304bdd229eb892696480b2558

The kexi master branch fails to build on Kubuntu CI with the errors in
the following log

https://launchpadlibrarian.net/328135944/buildlog_ubuntu-artful-amd64.kexi_1%3A3.0.1+p17.10+git20170710.1658-0_BUILDING.txt.gz

Seems to be an issue which occurs with the Qt 5.7.1 that we still have
in ubuntu artful for a short while, but not with Qt 5.9.1 when I did a
test build with that instead. Also explains why I did not see this
failure on Neon CI or build.kde.org

Regards

Rik Mills