[runtime] Avoid putting non-virtual and non-static DIM methods into v…

…tables, roslyn generates these for private property accessors.

Fixes part of mono#13374.

mono/metadata/object.c

@@ -1548,7 +1548,7 @@ build_imt_slots (MonoClass *klass, MonoVTable *vt, MonoDomain *domain, gpointer*
 				continue;
 			}
 
-			if (!(method->flags & METHOD_ATTRIBUTE_STATIC)) {
+			if (method->flags & METHOD_ATTRIBUTE_VIRTUAL) {
 				add_imt_builder_entry (imt_builder, method, &imt_collisions_bitmap, vt_slot, slot_num);
 				vt_slot ++;
 			}