fix: skip layout tests for types with unknown attributes

Types with unknown attributes (found_unknown_attr) may have unpredictable
layouts. Skip layout tests to prevent compile-time assertion failures.

Fixes #3319

Author: naoNao89

bindgen/codegen/mod.rs

@@ -2674,7 +2674,10 @@ impl CodeGenerator for CompInfo {
                 }
             }
 
-            if ctx.options().layout_tests && !self.is_forward_declaration() {
+            // Skip layout tests for types with unknown attributes that may affect layout.
+            // This prevents incorrect compile-time assertions for types like max_align_t
+            // where the layout may differ between platforms. See issue #3319.
+            if ctx.options().layout_tests && !self.is_forward_declaration() && !self.found_unknown_attr() {
                 if let Some(layout) = layout {
                     let compile_time = ctx.options().rust_features().offset_of;
                     let fn_name = if compile_time {