qtbase examples compile failure with enabled gui module and disabled opengl

make[1]: Entering directory '.../qt5base-5.9.1/examples/opengl'
cd hellowindow/ && ( test -e Makefile || .../qt5base-5.9.1/bin/qmake -o Makefile .../qt5base-5.9.1/examples/opengl/hellowindow/hellowindow.pro ) && make -f Makefile
make[2]: Entering directory '.../qt5base-5.9.1/examples/opengl/hellowindow'
.../host/bin/sparc-linux-g++ -c -pipe -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os --sysroot=.../host/sparc-buildroot-linux-uclibc/sysroot -O2 -O3 -fno-exceptions -Wall -W -D_REENTRANT -fPIC -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -I. -I../../../include/QtGui/5.9.1 -I../../../include/QtGui/5.9.1/QtGui -I../../../include -I../../../include/QtGui -I../../../include/QtCore/5.9.1 -I../../../include/QtCore/5.9.1/QtCore -I../../../include/QtCore -I.moc -I../../../mkspecs/devices/linux-buildroot-g++ -o .obj/hellowindow.o hellowindow.cpp
In file included from hellowindow.cpp:51:0:
hellowindow.h:96:5: error: 'QOpenGLShaderProgram' does not name a type
QOpenGLShaderProgram *m_program;
^~~~~~~~~~~~~~~~~~~~
hellowindow.h:97:5: error: 'QOpenGLBuffer' does not name a type
QOpenGLBuffer m_vbo;
^~~~~~~~~~~~~
hellowindow.cpp: In constructor 'Renderer::Renderer(const QSurfaceFormat&, Renderer*, QScreen*)':
hellowindow.cpp:62:40: error: invalid use of incomplete type 'class QOpenGLContext'
m_context = new QOpenGLContext(this);
^
In file included from ../../../include/QtGui/qsurfaceformat.h:1:0,
from ../../../include/QtGui/../../src/gui/kernel/qsurface.h:45,
from ../../../include/QtGui/qsurface.h:1,
from ../../../include/QtGui/../../src/gui/kernel/qwindow.h:51,
from ../../../include/QtGui/qwindow.h:1,
from ../../../include/QtGui/QWindow:1,
from hellowindow.h:51,
from hellowindow.cpp:51: