I don’t think there’s a way to control it, and I’d ask why you’d even need or want to. That file is an internal implementation detail of CMake and arguably shouldn’t even be mentioned in the documentation. The project should not be relying on that file having any particular name, nor try to reference or use it directly.
The project doesn’t need to explicitly include the cmake_pch.hxx file. CMake injects it on the compiler command line for you where needed. If it is creating a cmake_pch.hxx file, my recollection is that it means CMake thinks the source to use it with is a C++ file, not a C file. I think there are separate cmake_pch.h and cmake_pch.hxx files for C and C++ sources, but it’s been a while since I looked at that. @cristianadam would know the details and could comment further.