This setting should be set in the same way that it is set in linked Qt version. Qt4 is built with "/Zc:wchar_t-" setting and Qt5 with "Zc:wchar_t".
"Zc:wchar_t" is the default setting, so change is only needed to compile QuaZip against Qt4. IN CMake it may be achieved like that:
set_target_properties(quazip PROPERTIES COMPILE_FLAGS "/Zc:wchar_t-")
To support such feature in Visual Studio projects added to SVN, it is possible to define new build configurations; instead of 'Debug' and 'Release', they could be called 'Debug-Qt4', etc.
Possible problems when this flag is not set properly: