Then lib_xcore_math will be fetched which is undesirable. The parent project needs to be able to fetch (or submodule) lib_xcore_math in the manner it wishes.
lib_xcore_math must only be fetched by lib_mic_array when lib_mic_array is a top-level project.
If this CMakeLists is included in a parent project (via add_subdirectory): https://github.com/xmos/lib_mic_array/blob/develop/lib_mic_array/CMakeLists.txt
Then lib_xcore_math will be fetched which is undesirable. The parent project needs to be able to fetch (or submodule) lib_xcore_math in the manner it wishes.
lib_xcore_math must only be fetched by lib_mic_array when lib_mic_array is a top-level project.