Dont expect __qualname__ to exist (#41989)

lib/spack/spack/build_environment.py

@@ -1333,7 +1333,7 @@ def make_stack(tb, stack=None):
             # don't provide context if the code is actually in the base classes.
             obj = frame.f_locals["self"]
             func = getattr(obj, tb.tb_frame.f_code.co_name, "")
-            if func:
+            if func and hasattr(func, "__qualname__"):
                 typename, *_ = func.__qualname__.partition(".")
                 if isinstance(obj, CONTEXT_BASES) and typename not in basenames:
                     break