bump nix to 0.14 to fix compilation issues

[ryankurte]

Waiting on: nix-rust/nix#1060 (comment)
See also: rust-embedded/linux-embedded-hal#17
Patching to git source tested to be working

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @nastevens (or someone else) soon.

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[ryankurte]

nix 0.14.x has landed and CI seems happy ^_^

[posborne]

Was going to comment on MSRV stuff again but the MSRV here is 1.26.0 and the MSRV for nix is 1.24.1 so we should be good to go.

[posborne]

bors r+

^^^ TODO: repo hasn't been borsified yet.