Compile tests files with enabled exceptions, required for exiv2 0.27
Summary: This is a follow up of https://cgit.kde.org/gwenview.git/patch/?id=b81eed1dc4d879f06d651ea0954bee1b46c7947e to also make the tests build withour running into errors when building against exiv2 0.27.
Reviewers: Gwenview, ngraham
Reviewed By: Gwenview, ngraham
Subscribers: ngraham, Gwenview
Tags: Gwenview
Differential Revision: https://phabricator.kde.org/D19169