Make the configured namespace part of QT_BUILD_KEY_COMPAT too.
Make the configured namespace part of QT_BUILD_KEY_COMPAT too.

The eclipse integration is namespaced, but it still pulled in system plugins like the oxygen style through QT_BUILD_KEY_COMPAT check in QLibraryPrivate::isPlugin()

Task: 250185
Reviewed-by: dt <a5b10b69f8138684917b6497d164c14d2a2aa981@nokia.com>
BT: yes
(cherry picked from commit cca58cff45ea248ab9c65fd8ce088433af1c0fe0)

igor-sfdc/qt-wk,radekp/qt,radekp/qt,radekp/qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,RLovelett/qt,KDE/qt,radekp/qt,KDE/qt,KDE/qt,radekp/qt,igor-sfdc/qt-wk,KDE/qt,radekp/qt,RLovelett/qt,RLovelett/qt,radekp/qt,KDE/qt,radekp/qt,igor-sfdc/qt-wk,RLovelett/qt,RLovelett/qt,RLovelett/qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,KDE/qt,radekp/qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,KDE/qt,RLovelett/qt,igor-sfdc/qt-wk,RLovelett/qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,radekp/qt,RLovelett/qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,RLovelett/qt,RLovelett/qt,KDE/qt