Upgrade nix to 0.24, limit features

This removes memoffset as an indirect dependency, and decreases build times.

Author: rtzoeller

Cargo.toml

@@ -31,7 +31,7 @@ rand = "0.8"
 log = { version = "0.4", optional = true }
 
 [target.'cfg(unix)'.dependencies]
-nix = "0.23"
+nix = { version = "0.24", default-features = false, features = ["fs", "mman"] }
 libc = "0.2"
 
 [target.'cfg(windows)'.dependencies]