Update nix to 0.14

This is needed to fix breaking changes in libc on arm and s390x.
See: nix-rust/nix#1055

Author: cuviper

Cargo.toml

@@ -13,7 +13,7 @@ authors = ["[email protected]"]
 
 [dependencies]
 libc = "0.2.28"
-nix = "0.13"
+nix = "0.14"
 quick-error = "1.2.0"
 
 [dev-dependencies]