When building Qt in developer mode with unit testing enabled and configured with

-no-gui -no-widgets

, qtbase does not compile because the unit test in qtbase/tests/auto/corelib/serialization/qdatastream_core_pixmap requires the GUI module. 

This can be fixed by modified the lines 13-14 of qtbase/tests/auto/corelib/serialization/serialization.pro like this: 

!qtHaveModule(gui): SUBDIRS -= \
    qdatastream \
    qdatastream_core_pixmap

The same appears in all unit tests in the module qtxmlpatterns because of QT += gui in qtxmlpatterns/tests/auto/xmlpatterns.pri. It seems that this dependency is not detected in the configure script.

I've discovered this problem when building 5.12 but the serialization.pro is the same in 5.15, so I guess the problem still exists in the development branch