phonon fails to build: seeksliderplugin.h:50: Error: Undefined interface

[Colin Williams]

Any ideas on what steps I should take to proceed with the build?
_______________________________________________________________________________________________________

# kdesrc-build running: 'make' '-j' '8'
# from directory: /usr/local/kde/build/libraries/phonon
-- 

Installing in /usr/local/kde/usr. Run
/usr/local/kde/build/libraries/phonon/prefix.sh to set the environment
for Phonon.
-- Could not set up the appstream test. appstreamcli is missing.
-- The following OPTIONAL packages have been found:

 * Qt5UiPlugin (required version >= 5.15.2)
 * Qt5Xml (required version >= 5.15.2)
 * PkgConfig

-- The following RECOMMENDED packages have been found:

 * Qt5Designer (required version >= 5.15.0), Needed to build the Qt
Designer plugin, <https://www.qt.io/download>
 * PulseAudio (required version >= 0.9.15), A cross-platform,
networked sound server, <http://www.pulseaudio.org>
 * GLIB2, GLib 2 is required to compile the pulseaudio for Phonon,
<http://www.gtk.org/download/>

-- The following REQUIRED packages have been found:

 * ECM (required version >= 5.60), Extra CMake Modules,
<https://api.kde.org/frameworks/extra-cmake-modules/html/index.html>
 * Qt5Core (required version >= 5.15.0), Qt5 core module,
<https://www.qt.io/download>
 * Qt5Gui (required version >= 5.15.0), Qt5 GUI module,
<https://www.qt.io/download>
 * Qt5Widgets (required version >= 5.15.0), Qt5 widgets module,
<https://www.qt.io/download>

-- Configuring done
-- Generating done
-- Build files have been written to: /usr/local/kde/build/libraries/phonon
[  1%] Automatic MOC and UIC for target phonon4qt5
[  1%] Built target phonon4qt5_autogen
Consolidate compiler generated dependencies of target phonon4qt5
[  2%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/abstractaudiooutput.cpp.o
[  3%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/phonon4qt5_autogen/mocs_compilation.cpp.o
[  4%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/abstractmediastream.cpp.o
[  6%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/audiooutput.cpp.o
[  7%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/abstractvideooutput_p.cpp.o
[  8%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/audiodataoutput.cpp.o
[  9%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/abstractvideooutput.cpp.o
[ 11%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/abstractaudiooutput_p.cpp.o
[ 12%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/audiooutputinterface.cpp.o
[ 13%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/backendcapabilities.cpp.o
[ 14%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/effect.cpp.o
[ 16%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/effectparameter.cpp.o
[ 17%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/effectwidget.cpp.o
[ 18%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/factory.cpp.o
[ 19%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/globalconfig.cpp.o
[ 20%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/iodevicestream.cpp.o
[ 22%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/mediacontroller.cpp.o
[ 23%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/mediaobject.cpp.o
[ 24%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/medianode.cpp.o
[ 25%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/mediasource.cpp.o
[ 27%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/mrl.cpp.o
[ 28%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/objectdescription.cpp.o
[ 29%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/objectdescriptionmodel.cpp.o
[ 30%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/path.cpp.o
[ 32%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/phononnamespace.cpp.o
[ 33%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/platform.cpp.o
[ 34%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/pulsesupport.cpp.o
[ 35%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/seekslider.cpp.o
[ 37%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/statesvalidator.cpp.o
[ 38%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/streaminterface.cpp.o
[ 39%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/swiftslider.cpp.o
[ 40%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/volumefadereffect.cpp.o
[ 41%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/volumeslider.cpp.o
[ 43%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/videoplayer.cpp.o
[ 44%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/videowidget.cpp.o
[ 45%] Building CXX object
phonon/CMakeFiles/phonon4qt5.dir/ECMQmLoader-libphonon_qt.cpp.o
[ 46%] Building CXX object phonon/CMakeFiles/phonon4qt5.dir/pulsestream.cpp.o
[ 48%] Linking CXX shared library ../bin/libphonon4qt5.so
[ 48%] Built target phonon4qt5
[ 49%] Automatic MOC and UIC for target phononwidgets
[ 50%] Automatic MOC and UIC for target phononsettings
[ 51%] Automatic MOC and UIC for target phonon4qt5experimental

AutoMoc subprocess error
------------------------
The moc process failed to compile
  "SRC:/designer/seeksliderplugin.h"
into
  "BIN:/designer/phononwidgets_autogen/EWIEGA46WW/moc_seeksliderplugin.cpp"

Command
-------
/usr/local/share/Qt-5/bin/moc -DQT_CORE_LIB -DQT_DESIGNER_LIB
-DQT_GUI_LIB -DQT_NO_DEBUG -DQT_UIPLUGIN_LIB -DQT_WIDGETS_LIB
-DQT_XML_LIB -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE
-D_LARGEFILE64_SOURCE -Dphononwidgets_EXPORTS
-I/usr/local/kde/build/libraries/phonon/designer
-I/usr/local/kde/src/libraries/phonon/designer
-I/usr/local/kde/src/libraries/phonon
-I/usr/local/kde/build/libraries/phonon
-I/usr/local/kde/src/libraries/phonon/includes
-I/usr/local/kde/build/libraries/phonon/includes
-I/usr/local/kde/build/libraries/phonon/phonon
-I/usr/local/kde/src/libraries/phonon/phonon
-I/usr/local/share/Qt-5/include
-I/usr/local/share/Qt-5/include/QtUiPlugin
-I/usr/local/share/Qt-5/include/QtWidgets
-I/usr/local/share/Qt-5/include/QtGui
-I/usr/local/share/Qt-5/include/QtCore
-I/usr/local/share/Qt-5/mkspecs/linux-g++
-I/usr/local/share/Qt-5/include/QtDesigner
-I/usr/local/share/Qt-5/include/QtXml -I/usr/local/include
-I/usr/local/include/c++/11
-I/usr/local/include/c++/11/armv7l-cros-linux-gnueabihf
-I/usr/local/include/c++/11/backward
-I/usr/local/lib/gcc/armv7l-cros-linux-gnueabihf/11/include
-I/usr/local/lib/gcc/armv7l-cros-linux-gnueabihf/11/include-fixed
-I/usr/include --include
/usr/local/kde/build/libraries/phonon/designer/phononwidgets_autogen/moc_predefs.h
--output-dep-file -o
/usr/local/kde/build/libraries/phonon/designer/phononwidgets_autogen/EWIEGA46WW/moc_seeksliderplugin.cpp
/usr/local/kde/src/libraries/phonon/designer/seeksliderplugin.h

Output
------
/usr/local/kde/src/libraries/phonon/designer/seeksliderplugin.h:50:
Error: Undefined interface

make[2]: *** [designer/CMakeFiles/phononwidgets_autogen.dir/build.make:71:
designer/CMakeFiles/phononwidgets_autogen] Error 1
make[1]: *** [CMakeFiles/Makefile2:272:
designer/CMakeFiles/phononwidgets_autogen.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
[ 51%] Built target phononsettings_autogen
[ 51%] Built target phonon4qt5experimental_autogen
make: *** [Makefile:146: all] Error 2


_____________________________________________________________________________________________________