I expect it is necessary to keep build configuration portable with respect to packaging and environment configuration. In other words, I expect downloading from

I expect it is necessary to keep build configuration portable with respect to packaging and environment configuration. In other words, I expect downloading from URLs in Makefiles and CMakeLists to be a local maximum. Keeping a parallel set of instructions or metadata that includes specific URLs and such might work, though. As long as you can skip all that when a system package, filesystem path, or git submodule is more appropriate.