[QGIS-Developer] qgis 3.40.7 fails to build with py-sip6 6.12.0

[Greg Troxel]

Now that I'm building a maintained version: can anyone build with
py-sip6 6.12.0?  (With 6.10.0, 3.40 builds and runs fine.)

  sip-build: class 'Ui::Qgs25DRendererWidgetBase' has not been defined
  class 'Ui::QgsColorRampShaderWidgetBase' has not been defined
  class 'Ui::QgsDbSourceSelectBase' has not been defined
  class 'Ui::QgsLayerTreeEmbeddedConfigWidgetBase' has not been defined
  class 'Ui::QgsTextFormatWidgetBase' has not been defined
  class 'Ui::QgsTableWidgetUiBase' has not been defined
  class 'Ui::QgsRichTextEditorBase' has not been defined
  class 'Ui::QgsOWSSourceSelectBase' has not been defined
  class 'QgsTopologicalMesh::Changes' has not been defined
  ninja: build stopped: subcommand failed.
  *** Error code 1