py/objmodule: Workaround for MSVC with no module delegation.

When compiling mpy-cross, there is no `sys` module, and so there will
be no entries in the `mp_builtin_module_delegation_table`.

MSVC doesn't like this, so instead pretend as if the feature isn't
enabled at all.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

py/makemoduledefs.py

@@ -103,6 +103,9 @@ def generate_module_table_header(modules):
 
 
 def generate_module_delegations(delegations):
+    if not delegations:
+        return
+
     print("\n#define MICROPY_MODULE_DELEGATIONS \\")
     for obj_module, fun_name in delegations:
         print(

py/objmodule.c

@@ -230,7 +230,7 @@ mp_obj_t mp_module_get_builtin(qstr module_name, bool extensible) {
 }
 
 STATIC void module_attr_try_delegation(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
-    #if MICROPY_MODULE_ATTR_DELEGATION
+    #if MICROPY_MODULE_ATTR_DELEGATION && defined(MICROPY_MODULE_DELEGATIONS)
     // Delegate lookup to a module's custom attr method.
     size_t n = MP_ARRAY_SIZE(mp_builtin_module_delegation_table);
     for (size_t i = 0; i < n; ++i) {