mypyc assertion error when generating `__ne__` from inherited `__eq__` in package import cycle

**Bug Report** mypyc can fail with an internal `AssertionError` when it tries to generate `__ne__` from an inherited `__eq__`. This happens when the inherited method's declaration is available before its `FuncIR` body has been generated. One way to trigger this is with a package import cycle where `__init__.py` imports a child module before importing the subpackage that defines the base class. **To Reproduce** Add this test case to `mypyc/test-data/run-multimodule.test`: ``` [case testPackageCycleInheritedEq] from other.other_child import Child def make_child() -> Child: return Child() [file other/__init__.py] from other.other_child import Child as Child from other.other_subpkg import Base as Base [file other/other_child.py] from other.other_subpkg import Base class Child(Base): pass [file other/other_subpkg/__init__.py] from other.other_subpkg.other_base import Base as Base [file other/other_subpkg/other_base.py] class Base: def __eq__(self, other: object) -> bool: return True [file driver.py] from native import make_child left = make_child() right = make_child() assert left == right assert not (left != right) ``` Run: ``` python -m pytest -q mypyc/test/test_run.py -k testPackageCycleInheritedEq ``` **Expected Behavior** mypyc should compile this successfully. Since `Child` inherits `Base.__eq__` but does not define `__ne__`, mypyc should be able to synthesize `Child.__ne__` from the inherited `__eq__` declaration. **Actual Behavior** mypyc fails with an internal assertion error while generating `__ne__`: ``` mypyc/irbuild/classdef.py:...: in gen_glue_ne_method assert func_ir AssertionError ``` **Your Environment** - Mypy version used: Built from latest commit in master. - Mypy command-line flags: Irrelevant. See provided test. Fix incoming. - Mypy configuration options from `mypy.ini` (and other config files): None - Python version used: Python 3.12