Unix `ar` archive labels, entry kinds, and extension helpers.
This crate is part of the `use-archive` facade workspace. It exposes `ar`-specific primitive labels only. It does not parse static libraries, Debian packages, symbol tables, or archive members.
```rust
use use_ar::{ArEntryKind, ArFormat, is_ar_filename};
assert!(is_ar_filename("libexample.a"));
assert_eq!(ArFormat::Gnu.as_str(), "gnu");
assert_eq!(ArEntryKind::SymbolTable.as_str(), "symbol-table");
```