changing cmake variable while generating cmake project

If you modify a cmake variable while qtcreator is configuring/generating the cmake project ('apply configuration changes' button), the generation does not stop, the variable modification is not taken into account (nothing surprising) BUT the project configuration is modified, and you cannot change the variable from the gui anymore.

The only solution I found was to edit manually both CMakeLists.txt.user and CMakeCache.txt to change the variable. Then everything goes back in order.

Locking cmake variables while generating the project can be a solution.

I am surprised that CMakeLists.txt.user is storing these informations as they are redundant with the CMakeCache.txt, is it really necessary?