Merge pull request godotengine#1958 from dsnopek/rid-alignment

Fix alignment on `RID` and other classes that use `uint8_t opaque[SIZE]`

Author: dsnopek

binding_generator.py

@@ -768,7 +768,10 @@ def generate_builtin_class_header(builtin_api, size, used_classes, fully_used_cl
 
     result.append(f"class {class_name} {{")
     result.append(f"\tstatic constexpr size_t {snake_class_name}_SIZE = {size};")
-    result.append(f"\tuint8_t opaque[{snake_class_name}_SIZE] = {{}};")
+    # We don't get alignment information from the JSON so we have to guess.
+    # This logic should be correct for all built-in types as they exist right now.
+    alignment = 8 if size >= 8 else 4
+    result.append(f"\talignas({alignment}) uint8_t opaque[{snake_class_name}_SIZE] = {{}};")
 
     result.append("")
     result.append("\tfriend class Variant;")