CMake custom IAR toolchain issues

[signal cedar]

[posting here, because there is an open thread on #tooling that I don't want to interrupt]

I have added a custom toolchain for my IAR compiler suite following these instructions:
https://github.com/IARSystems/cmake-tutorial

I still have a few other CMake issues, but when I now run CMake pointing it at this toolchain file, I get the following messages

CMake Error: Could not find cmake module file: CMakeDetermineCPPCompiler.cmake
CMake Error: Could not find cmake module file: C:/Projects/xxx/out/build/EWARM/CMakeFiles/3.26.1/CMakeCPPCompiler.cmake
CMake Error: Could not find cmake module file: CMakeCPPInformation.cmake
CMake Error: Could not find cmake module file: CMakeTestCPPCompiler.cmake

CMake appears to get past these issues and carries on, but these messages have me worried.
Anyone with any idea what CMake is trying to tell me?
And what I can do about it?

I found this article: https://stackoverflow.com/questions/61814019/getting-could-not-find-cmake-module-file-cmakedetermineversioncompiler-cmake

Almost similar, and the problem seems routed in a simple typo in the CMakeLists.txt.

[opaque mica]

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[signal cedar]

I did have to make a modification to this toolchain file.
Out of the box it only does

find_program(CMAKE_CXX_COMPILER ...)

But then I get a CMake error No CMAKE_CPP_COMPILER could be found

So I duplicated that instruction underneath the existing one and change its var to

find_program(CMAKE_CPP_COMPILER ...)

Does CMake require both?
Is one obsoleted?

[signal cedar]

I am dumb.
The top level CMakeLists.txt file reads

project(SourceSimulator LANGUAGES CPP)

That should of course read CXX.

!solved