With riot-wrappers ceasing to depend on exported variables in https://github.com/RIOT-OS/rust-riot-wrappers/pull/79, the door is open for stopping the re-export of variables and setting links="riot-sys" (which as a matter of fact we don't do: We don't link it in, we merely provide a static library to be combined with it).
This is a breaking change, and would make a 0.8; nonetheless, riot-wrappers could stay compatible with 0.7 and 0.8 simultaneously (we may not want it to because it won't be tested, but it's convenient that riot-wrappers doesn't really need to change -- it can just stop using something riot-sys provides before riot-sys jumps the version and stops providing it).