Fails to build: Could NOT find Qt6Quick

vtk-9.3.0-8 fails to build due to CMake configure error:

-- Could NOT find Qt6Quick (missing: Qt6Quick_DIR)
CMake Warning at CMake/vtkModule.cmake:4787 (find_package):
  Found package configuration file:

    /usr/lib/cmake/Qt6/Qt6Config.cmake

  but it set Qt6_FOUND to FALSE so package "Qt6" is considered to be NOT
  FOUND.  Reason given by package:

  Failed to find required Qt component "Quick".

  Expected Config file at "/usr/lib/cmake/Qt6Quick/Qt6QuickConfig.cmake" does
  NOT exist



  Configuring with --debug-find-pkg=Qt6Quick might reveal details why the
  package was not found.

  Configuring with -DQT_DEBUG_FIND_PACKAGE=ON will print the values of some
  of the path variables that find_package uses to try and find the package.

Call Stack (most recent call first):
  GUISupport/QtQuick/CMakeLists.txt:17 (vtk_module_find_package)


CMake Error at CMake/vtkModule.cmake:4793 (message):
  Could not find the Qt6 external dependency.
Call Stack (most recent call first):
  GUISupport/QtQuick/CMakeLists.txt:17 (vtk_module_find_package)


-- Configuring incomplete, errors occurred!
==> ERROR: A failure occurred in build().
    Aborting...

The PKGBUILD specifies qt5- packages in depends, but other dependencies already pull in qt6- variants and CMake picks the newer version.