[CMake] Which style of file extension is better for optional CMake files?

[Ryuan Choi]

> I think it's mostly a matter of style... so you could go either way.
> 
> Personally, I would choose the "PlatformXXX.cmake" names over the
> other ones. The other ones are too close to "CMakeLists.txt" and could
> be confused for them by a quick scan of the file name. So, for human
> readability and understanding, I would prefer the PlatformXXX.cmake
> names.

Thank you for the answer.
I realized that I have a mistake in my question.
For now, we are using CMakeListsXXX.txt which CMakeLists.txt include - not CMakeListsXXX.cmake. sorry for my typo.
All of them are list of source, but CMakeListsXXX.txt is optional.
My bug is to change CMakeListsXXX.txt to PlatformXXX.cmake because I didn't see CMakeListsXXX.txt

As you mentioned, if I can choose anything, I'll keep the current.

Best Regards,
Ryuan Choi