Add test coverage to ansiballz builder source mapping (#85382)

Should bring code coverage in _builder.py to 100%.

test/units/_internal/_ansiballz/test_builder.py

@@ -0,0 +1,22 @@
+from __future__ import annotations
+
+from ansible._internal._ansiballz._builder import ExtensionManager
+from ansible.module_utils._internal._ansiballz._extensions import _pydevd
+
+
+def test_debugger_source_mapping() -> None:
+    """Synthetic coverage for builder source mapping."""
+    debug_options = _pydevd.Options(source_mapping={
+        "ide/path.py": "controller/path.py",
+        "ide/something.py": "controller/not_match.py",
+    })
+
+    manager = ExtensionManager(debug_options)
+    manager.source_mapping.update({
+        "controller/path.py": "zip/path.py",
+        "controller/other.py": "not_match.py",
+    })
+
+    extensions = manager.get_extensions()
+
+    assert extensions['_pydevd']['source_mapping'] == {'controller/other.py': 'not_match.py', 'ide/path.py': 'zip/path.py'}