Oh, I have not tried using it from system repositories: I tried that with another library (in a hobby project) before, had issues with that, been told and generally gathered that it is easier to pull dependencies with cargo, so went straight to that this time. I see that librust-clap-dev would pull 157 other packages with it though, but will look more closely into it: I would actually prefer getting dependencies from system repositories, thanks for pointing it out.
As for newer compilers, I prefer to depend on system repositories and package manager for updates, and to stick to stable branches, so that things do not change too often. I see the appeal of rolling release distributions and cutting edge software, but not feeling comfortable using it for things that are supposed to be reliable.