Qt currently fails to set QT_NO_EXCEPTIONS when building with Clang. The Clang documentation suggests it should happen across platforms but in practice it seems to happen only when targeting Mac. (ICC apparently masquerades as clang so may be affected too.)
This patch corrects that omission which leads to issues like this one: https://git.reviewboard.kde.org/r/130139/
I have attempted to add the corresponding unsetters to the file and target specific exceptions enabler macros; they have the intended effect on the compiler invocation.
I have filed a Qt bug report (https://bugreports.qt.io/browse/QTBUG-61034) but I doubt a fix would land before 5.9.1 . IOW, we'll still want to take care of this in the ECM.