QT_STATIC must be defined for static builds to have the right
import/export symbol macros defined. Originally, this macro is wrapped
in a condition. That's why we extend qt_feature_definition to be able
to write a prerequisite to qconfig.h.
Change-Id: I610e60acc7f5bdc031eff6d53a76e0b229a5c8c2
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>