Explicity close() bench lib

Windows has been exhibiting crashes after completion. We hope to
explicilty control dll close in order to either prevent problems or get
more explicit information on problems.

Author: posborne

crates/cli/src/benchmark.rs

@@ -311,6 +311,12 @@ impl BenchmarkCommand {
                 drop((engine, module));
                 all_measurements.extend(measurements.finish());
             }
+
+            // Explicitly close the library to handle any unload errors.
+            // We log errors but don't fail since measurements have been collected.
+            if let Err(e) = lib.close() {
+                log::warn!("Error unloading library: {e}");
+            }
         }
 
         // If we are only benchmarking one phase then filter out any