[PATCH] [clang][frontend] Fix AllocKind retrieving for

`CXXConstructorDecl` refs #132794

When getting the `ExplicitSpecifier` of the `CXXConstructorDecl`, one
of the canonical declaration is returned. When writing the declaration
record with `ExplicitSpecifier`, the `AllocKind` of the canonical
declaration has to be used.
If this is not done it will later crash when on deserialization.

Author: koplas

clang/include/clang/AST/DeclCXX.h

@@ -2601,10 +2601,11 @@ class CXXConstructorDecl final
   void anchor() override;
 
   size_t numTrailingObjects(OverloadToken<InheritedConstructor>) const {
-    return CXXConstructorDeclBits.IsInheritingConstructor;
+    return getCanonicalDecl()->CXXConstructorDeclBits.IsInheritingConstructor;
   }
   size_t numTrailingObjects(OverloadToken<ExplicitSpecifier>) const {
-    return CXXConstructorDeclBits.HasTrailingExplicitSpecifier;
+    return getCanonicalDecl()
+        ->CXXConstructorDeclBits.HasTrailingExplicitSpecifier;
   }
 
   ExplicitSpecifier getExplicitSpecifierInternal() const {