top-level configure returns with exit code != 0 if qt3d is checked out

How to reproduce

Checkout

• the top-level repo at ed139ea47e21984e64a130b167ed715adf319234
• qtbase at 4e5f203df63740d6a00c67d47b961ce04e740057
• qt3d at 598b72dac2f467fcc244e0b7ef348c034daf428b

Now configure a top-level build with our configure script.
You may -skip qt3d.

What happens?

The configure script ends with the output

-- Configuring done
-- Generating done

but the exit code is not zero.

The actual build (of just qtbase) works fine.

A top-level build with plain cmake does not exhibit this behavior.

Analysis

Further up, one sees the following output:

CMake Error: Error required internal CMake variable not set, cmake may not be built correctly.
Missing variable is:
CMAKE_FIND_LIBRARY_PREFIXES
CMake Error: Error required internal CMake variable not set, cmake may not be built correctly.
Missing variable is:
CMAKE_FIND_LIBRARY_SUFFIXES

This stems from the cmake -P call that runs QtProcessConfigureArgs.cmake.

One of the configure.cmake files of qt3d gained a find_package call, leading to this error: https://codereview.qt-project.org/c/qt/qt3d/+/339049

QtProcessConfigureArgs.cmake defines stubs for qt_find_package but not the plain CMake find_package.