Handle archived dylibs on AIX (#2442)

In recent Rust versions, the dylib format for AIX has changed to reflect
that shared libraries on AIX are normal archived, in the Big archive
format.
See rust-lang/rust#132362.

However, Python wheels on the platforms still use un-archived shared
objects, so this change updates module_writer to unarchive the archived
dylib before we copy it over to the wheel.

Author: daltenty

src/module_writer.rs

@@ -793,6 +793,28 @@ fn handle_cffi_call_result(
     }
 }
 
+// Extract the shared object from a AIX big library archive
+fn unpack_big_archive(target: &Target, artifact: &Path, temp_dir_path: &Path) -> Result<PathBuf> {
+    // Newer rust generates archived dylibs on AIX, as shared
+    // libraries are typically archived on the platform.
+    if target.cross_compiling() {
+        bail!("can't unpack big archive format while cross_compiling")
+    }
+    debug!("Unpacking archive {}", artifact.display());
+    let mut ar_command = Command::new("ar");
+    ar_command
+        .current_dir(temp_dir_path)
+        .arg("-X64")
+        .arg("x")
+        .arg(artifact);
+    let status = ar_command.status().expect("Failed to run ar");
+    if !status.success() {
+        bail!(r#"ar finished with "{}": `{:?}`"#, status, ar_command,)
+    }
+    let unpacked_artifact = temp_dir_path.join(artifact.with_extension("so").file_name().unwrap());
+    Ok(unpacked_artifact)
+}
+
 /// Copies the shared library into the module, which is the only extra file needed with bindings
 #[allow(clippy::too_many_arguments)]
 #[instrument(skip_all)]
@@ -825,6 +847,28 @@ pub fn write_bindings_module(
         python_interpreter.get_library_name(ext_name)
     };
 
+    let artifact_is_big_ar =
+        target.is_aix() && artifact.extension().unwrap_or(OsStr::new(" ")) == OsStr::new("a");
+    let temp_dir = if artifact_is_big_ar {
+        Some(tempfile::tempdir()?)
+    } else {
+        None
+    };
+    let artifact_buff = if artifact_is_big_ar {
+        Some(unpack_big_archive(
+            target,
+            artifact,
+            temp_dir.as_ref().unwrap().path(),
+        )?)
+    } else {
+        None
+    };
+    let artifact = if artifact_is_big_ar {
+        artifact_buff.as_ref().unwrap()
+    } else {
+        artifact
+    };
+
     if !editable {
         write_python_part(writer, project_layout, pyproject_toml)
             .context("Failed to add the python module to the package")?;

src/target.rs

@@ -616,6 +616,12 @@ impl Target {
         self.os == Os::Hurd
     }
 
+    /// Returns true if we're building a binary for AIX
+    #[inline]
+    pub fn is_aix(&self) -> bool {
+        self.os == Os::Aix
+    }
+
     /// Returns true if the current platform's target env is Musl
     #[inline]
     pub fn is_musl_libc(&self) -> bool {