How is CMAKE_<LANG>_COMPILER_AR determined automatically?

For context, I am a newcomer to CMake with a build that I observe failing on x86_64-darwin complaining that CMAKE_CXX_COMPILER_AR is not found, but the same build does not fail on x86_64-linux. Now, there are a lot of layers I still need to peel back before I can understand my issue, but I’d like to start with a simple question that I haven’t been able to figure out:

How is CMAKE_<LANG>_COMPILER_AR computed by default, and where in the CMake code can I look to find this logic?

Thank you in advance!


This usually means that Xcode is not installed/found IIRC. Are they using something like Homebrew or expecting to use the Xcode toolchain?