[CMake] Build flags when using Qt plugins (was: Where is QT_USE_IMPORTED_TARGETS not safe to use?)

[Stephen Kelly]

Clinton Stimpson wrote:

>> 
>> The output is attached, but I'm not certain it's very helpful. Let me
>> know if anything else would be useful. I can maybe try to create a
>> smaller plugin using qt example for easy reproduction of the issue.
> 
> What is CMAKE_BUILD_TYPE set to?

I think it should be the default. Will have to check (no windows VM, will 
have to reboot).