cffi: run stubtest on Windows (#9178)

stubs/cffi/cffi/api.pyi

@@ -72,6 +72,7 @@ class FFI:
     @overload
     def gc(self, cdata: CData, destructor: None, size: int = ...) -> None: ...
     def verify(self, source: str = ..., tmpdir: str | None = ..., **kwargs: Any) -> _cffi_backend.Lib: ...
+    # Technically exists on all OSs, but crashes on all but Windows. So we hide it in stubs
     if sys.platform == "win32":
         def getwinerror(self, code: int = ...) -> tuple[int, str] | None: ...