adding a working rlib autodiff test

tests/run-make/autodiff/rlib/dep.rs

@@ -0,0 +1,7 @@
+pub fn f(x: f64, y: f64) -> f64 {
+    2.0 * x + y
+}
+
+pub fn g(x: f64) -> f64 {
+    2.0 * x
+}

tests/run-make/autodiff/rlib/lib.rs

@@ -0,0 +1,13 @@
+#![feature(autodiff)]
+extern crate simple_dep;
+use std::autodiff::*;
+
+#[inline(never)]
+pub fn f2(x: f64) -> f64 {
+    x.sin()
+}
+
+#[autodiff_forward(df1_lib, Dual, Dual)]
+pub fn _f1(x: f64) -> f64 {
+    simple_dep::f(x, x) * f2(x)
+}

tests/run-make/autodiff/rlib/main.rs

@@ -0,0 +1,8 @@
+extern crate foo;
+
+fn main() {
+    //dbg!("Running main.rs");
+    let enzyme_y1_lib = foo::df1_lib(1.5, 1.0);
+    println!("output1: {:?}", enzyme_y1_lib.0);
+    println!("output2: {:?}", enzyme_y1_lib.1);
+}

tests/run-make/autodiff/rlib/rmake.rs

@@ -0,0 +1,66 @@
+//@ needs-enzyme
+//@ ignore-cross-compile
+
+use run_make_support::{cwd, run, rustc};
+
+fn main() {
+    // Build the dependency crate.
+    rustc()
+        .input("dep.rs")
+        .arg("-Zautodiff=Enable")
+        .arg("--edition=2024")
+        .arg("-Copt-level=3")
+        .arg("--crate-name=simple_dep")
+        .arg("-Clinker-plugin-lto")
+        .arg("--crate-type=lib")
+        .emit("dep-info,metadata,link")
+        .run();
+
+    let cwd = cwd();
+    let cwd_str = cwd.to_string_lossy();
+
+    let mydep = format!("-Ldependency={cwd_str}");
+
+    let simple_dep_rlib =
+        format!("--extern=simple_dep={}", cwd.join("libsimple_dep.rlib").to_string_lossy());
+
+    // Build the main library that depends on `simple_dep`.
+    rustc()
+        .input("lib.rs")
+        .arg("-Zautodiff=Enable")
+        .arg("--edition=2024")
+        .arg("-Copt-level=3")
+        .arg("--crate-name=foo")
+        .arg("-Clinker-plugin-lto")
+        .arg("--crate-type=lib")
+        .emit("dep-info,metadata,link")
+        .arg(&mydep)
+        .arg(&simple_dep_rlib)
+        .run();
+
+    let foo_rlib = format!("--extern=foo={}", cwd.join("libfoo.rlib").to_string_lossy());
+
+    // Build the final binary linking both rlibs.
+    rustc()
+        .input("main.rs")
+        .arg("-Zautodiff=Enable")
+        .arg("--edition=2024")
+        .arg("-Copt-level=3")
+        .arg("--crate-name=foo")
+        .arg("-Clto=fat")
+        .arg("--crate-type=bin")
+        .emit("dep-info,link")
+        .arg(&mydep)
+        .arg(&foo_rlib)
+        .arg(&simple_dep_rlib)
+        .run();
+
+    // Run the binary and check its output.
+    let binary = run("foo");
+    assert!(binary.status().success(), "binary failed to run");
+
+    let binary_out = binary.stdout();
+    let output = String::from_utf8_lossy(&binary_out);
+    assert!(output.contains("output1: 4.488727439718245"));
+    assert!(output.contains("output2: 3.3108023673168265"));
+}