Qt6: Fix MinGW build

src/Gui/CMakeLists.txt

@@ -70,13 +70,6 @@ if(MSVC)
          ${OPENGL_gl_LIBRARY}
     )
 
-    if(FREECAD_QT_MAJOR_VERSION EQUAL 6)
-        list(APPEND FreeCADGui_LIBS
-            Qt6::GuiPrivate
-        )
-    endif()
-
-
     if(FREECAD_USE_3DCONNEXION)
         list(APPEND FreeCADGui_LIBS
             hid
@@ -93,6 +86,14 @@ else(MSVC)
     )
 endif(MSVC)
 
+if (WIN32)
+    if(FREECAD_QT_MAJOR_VERSION EQUAL 6)
+        list(APPEND FreeCADGui_LIBS
+            Qt6::GuiPrivate
+        )
+    endif()
+endif()
+
 include_directories(
     ${QtCore_INCLUDE_DIRS}
     ${QtWidgets_INCLUDE_DIRS}

src/Gui/MainWindow.cpp

@@ -52,6 +52,7 @@
 # include <QToolBar>
 # include <QUrlQuery>
 # include <QWhatsThis>
+# include <QWindow>
 # include <QPushButton>
 #endif