Use GNU format tarballs to support longer paths

This fixes errors related to paths being too long, which is common when
using git dependencies. Note that cargo itself switched from UStar to
GNU format in 2020.

    thread 'main' panicked at src/main.rs:290:32:
        called `Result::unwrap()` on an `Err` value: Custom { kind: Other, error: "provided value is too long when setting path for some-crate-0.123.123/src/" }

Cargo.toml

@@ -22,7 +22,7 @@ flate2 = "1.0.22"
 openssl = { version = '0.10.41', optional = true }
 serde = { version = "1.0.104", features = ['derive'] }
 serde_json = "1.0.46"
-tar = "0.4.26"
+tar = "0.4.43"
 url = "2.1.1"
 
 [dev-dependencies]

src/main.rs

@@ -15,7 +15,7 @@ use std::fs::{self, File};
 use std::io;
 use std::io::prelude::*;
 use std::path::{self, Path, PathBuf};
-use tar::{Builder, Header};
+use tar::Builder;
 use url::Url;
 
 #[derive(Deserialize)]
@@ -285,13 +285,7 @@ fn build_ar(ar: &mut Builder<GzEncoder<File>>, pkg: &Package, config: &GlobalCon
             relative
         );
 
-        let mut header = Header::new_ustar();
-        let metadata = file.metadata().unwrap();
-        header.set_path(&path).unwrap();
-        header.set_metadata(&metadata);
-        header.set_cksum();
-
-        ar.append(&header, &mut file).unwrap();
+        ar.append_file(&path, &mut file).unwrap();
     }
 }