It is a little unfortunate, but Rust isn't blind to the problem. The community is converging on everyone using rustup (e.g. as of a few weeks ago, the install page recommends it https://www.rust-lang.org/en-US/install.html ) because it makes managing things like cross compilation[0] and upgrading stable compilers much easier. It also makes working with pinned compiler versions smoother: run `rustup override set nightly-2017-01-05` (or whatever date is recommended) in the project's directory, and that single command will both install that compiler and ensure it is used for the project (and only that project) when one invokes cargo or rustc. (I think it's great that Alacritty even helps people with the process, as I guess you noticed: https://github.com/jwilm/alacritty#prerequisites )
In any case, the nightly split is Rust deciding that it is good to allow people to use experimental features (i.e. working out if they're good/bug free) while also resisting infecting code that doesn't want to risk breakage---such projects use a stable compiler meaning even their dependencies won't be able to accidentally rely on something unstable---and thus hopefully avoiding defacto stabilisation of low quality features.