cmake -DFEATURE_gui=OFF -G Ninja -DCMAKE_INSTALL_PREFIX:PATH=/home/qt/RTA/src-6.9.0/qtbase /home/qt/RTA/src-6.9.0 

...
[QtWebEngine]     QT_FEATURE_xml=ON.
[QtWebEngine]     QT_FEATURE_xmlstream=ON.
[QtWebEngine]     QT_FEATURE_xmlstreamreader=ON.
[QtWebEngine]     QT_FEATURE_xmlstreamwriter=ON.
[QtWebEngine]     QT_FEATURE_zstd=ON.
CMake Error at qtbase/cmake/QtFeature.cmake:419 (message):
  Attempting to evaluate feature xcb but its definition is missing.  Either
  the feature does not exist or a dependency to the module that defines it is
  missing
Call Stack (most recent call first):
  qtbase/cmake/QtFeature.cmake:184 (qt_evaluate_feature)
  qtbase/cmake/QtFeature.cmake:223 (qt_internal_evaluate_config_expression)
  qtwebengine/cmake/QtConfigureHelpers.cmake:154 (qt_evaluate_config_expression)
  qtwebengine/configure.cmake:429 (qt_webengine_configure_check)
  qtwebengine/cmake/QtConfigureHelpers.cmake:12 (include)
  qtwebengine/src/CMakeLists.txt:14 (qt_webengine_run_configure)
-- Configuring incomplete, errors occurred!