CMake CPU detect

These CMake functions detect the CPU arch for Intel CPUs on Linux, MacOS and Windows. We focused on Intel CPUs since the Intel compilers (including Intel oneAPI) don't currently have automatic CPU detection. To use -march= features of Intel compilers, -march=native is undocumented and does not actually detect the CPU arch. For CMake with Intel compilers these functions help yield better runtime performance by enabling the features of the Host CPU. The same technique could be used for AMD, ARM, CUDA, etc. in the future.

Result variables

The variable HOST_ARCH is set in the parent scope. HOST_ARCH is empty if CPU arch is not known.

Demo

cmake -B build

will print the CPU family e.g. "icelake-client".