CMAKE_CONFIGURE_DEPENDS with newly created file

I have some code that is auto generated externally using another script.
Let’s say this generated in resources. In there, there is a “README.TXT” file with the generation timestamp, so the file changes every time the generation step is run.

I then have a CMake script include this auto generated code.
If there is no auto generated code yet, there is a static fallback option.
To ensure we always have the latest code, the following code has been added in the CMakeLists.txt:

If I already had auto generated code and I re-run the generation, at next build CMake reconfigures, all is well.
If I remove the generated files, CMake re-run and the fallback files are used.
However, if I have no generated files (resources and README.TXT do not exist) and I run the generation, then at next build CMake is not run.

Is that a known “limitation” of CMAKE_CONFIGURE_DEPENDS?
The documentation only talks about modification to the file, but it is not clear if creating the file is a modification.
If it is not possible using CMAKE_CONFIGURE_DEPENDS, what would be another way to do this?

I feel like it would be more useful to have an add_custom_command which copies the resources into the right location based on whether the static files are more up-to-date. If you’re using execute_process to make them, converting that to add_custom_command sounds like an even better solution. I don’t think trying to involve your configure step into your build is a wise decision since it feels like it’d be easy to end up with an infinite loop.