ext: Update pybind11 to v2.8.1

Change-Id: Ia1c7081377f53fd470addf35526f8b28a949a7b0
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52523
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Gabe Black <gabe.black@gmail.com>

ext/pybind11/tests/test_eval.py

@@ -4,7 +4,6 @@ import os
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import eval_ as m
 
 
@@ -33,3 +32,20 @@ def test_eval_empty_globals():
     g = {}
     assert "__builtins__" in m.eval_empty_globals(g)
     assert "__builtins__" in g
+
+
+def test_eval_closure():
+    global_, local = m.test_eval_closure()
+
+    assert global_["closure_value"] == 42
+    assert local["closure_value"] == 0
+
+    assert "local_value" not in global_
+    assert local["local_value"] == 0
+
+    assert "func_global" not in global_
+    assert local["func_global"]() == 42
+
+    assert "func_local" not in global_
+    with pytest.raises(NameError):
+        local["func_local"]()