To cross build Qt for QNX, VxWorks, Integrity one needs to make a host build on Desktop Linux. Those platforms doesn't support wayland, so theoretically -skip qtwayland can be used both on host and platform build, but it results in:

{{-- [QtBase] Searching for tool 'Qt6::qtwaylandscanner' in package Qt6WaylandScannerTools.
– Could NOT find Qt6WaylandScannerTools (missing: Qt6WaylandScannerTools_DIR)
CMake Error at qtbase/cmake/QtToolHelpers.cmake:799 (message):
  Failed to find the host tool "Qt6::qtwaylandscanner".  It is part of the
  Qt6WaylandScannerTools package, but the package could not be found.  Make
  sure you have built and installed the host WaylandScanner module, which
  will ensure the creation of the Qt6WaylandScannerTools package.
Call Stack (most recent call first):
  qtbase/cmake/QtToolHelpers.cmake:83 (qt_internal_find_tool)
  qtbase/src/tools/qtwaylandscanner/CMakeLists.txt:11 (qt_internal_add_tool)}}

The workaround is to install Qt for Linux Desktop using maintenance tool and configure with -DQt6WaylandScannerTools_DIR=/home/user/Qt/6.10.0/gcc_64/lib/cmake/Qt6WaylandScannerTools