test: add libstdc++ __debug check

Author: Nerixyz

lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/unordered/TestDataFormatterGenericUnordered.py

@@ -126,6 +126,14 @@ def test_with_run_command_libstdcpp(self):
         self.build(dictionary={"USE_LIBSTDCPP": 1})
         self.do_test_with_run_command()
 
+    @add_test_categories(["libstdcxx"])
+    @expectedFailureAll  # unordered __debug containers are not supported yet
+    def test_with_run_command_libstdcxx_debug(self):
+        self.build(
+            dictionary={"USE_LIBSTDCPP": 1, "CXXFLAGS_EXTRAS": "-D_GLIBCXX_DEBUG"}
+        )
+        self.do_test_with_run_command()
+
     @add_test_categories(["libc++"])
     def test_with_run_command_libcpp(self):
         self.build(dictionary={"USE_LIBCPP": 1})