feat: codex-linux-sandbox standalone executable (#740)

This introduces a standalone executable that run the equivalent of the
`codex debug landlock` subcommand and updates `rust-release.yml` to
include it in the release.

The idea is that we will include this small binary with the TypeScript
CLI to provide support for Linux sandboxing.

codex-rs/cli/Cargo.toml

@@ -7,6 +7,14 @@ edition = "2021"
 name = "codex"
 path = "src/main.rs"
 
+[[bin]]
+name = "codex-linux-sandbox"
+path = "src/linux-sandbox/main.rs"
+
+[lib]
+name = "codex_cli"
+path = "src/lib.rs"
+
 [dependencies]
 anyhow = "1"
 clap = { version = "4", features = ["derive"] }