Pass correct argument to rustc -Z ls

Behavior was changed back in rustc 1.74.

Fixes #2290

src/compiler/rust.rs

@@ -2372,7 +2372,7 @@ impl RlibDepReader {
         trace!("Discovering dependencies of {}", rlib.display());
 
         let mut cmd = process::Command::new(&self.executable);
-        cmd.args(["-Z", "ls"])
+        cmd.args(["-Z", "ls=root"])
             .arg(rlib)
             .env_clear()
             .envs(env_vars.to_vec())
@@ -3108,6 +3108,19 @@ proc_macro false
         assert_eq!(res[2], "lucet_runtime_macros");
     }
 
+    #[cfg(feature = "dist-client")]
+    #[test]
+    fn test_rlib_dep_reader() {
+        let cargo_home = std::env::var("CARGO_HOME");
+        assert!(cargo_home.is_ok());
+
+        let mut rustc_path = PathBuf::from(cargo_home.unwrap());
+        rustc_path.push("bin");
+        rustc_path.push("rustc");
+        let rlib_dep_reader = RlibDepReader::new_with_check(rustc_path, &[]);
+        assert!(rlib_dep_reader.is_ok());
+    }
+
     fn mock_dep_info(creator: &Arc<Mutex<MockCommandCreator>>, dep_srcs: &[&str]) {
         // Mock the `rustc --emit=dep-info` process by writing
         // a dep-info file.