Use FetchContent_MakeAvailable

[LecrisUT]

It is highly recommended to use FetchContent_MakeAvailable instead of manually interfacing with the FetchContent_Populate

[jbeder]

For reference:

The FetchContent_Populate() command is a self-contained call which can be used to perform content population as an isolated operation. It is rarely the right command to use, projects should almost always use FetchContent_Declare() and FetchContent_MakeAvailable() instead. The main use case for FetchContent_Populate() is in CMake script mode as part of implementing some other higher level custom feature.