libstdc++: fix incomplete type in v8::internal::is_subtype<T, U>

Using std::convertible with incomplete types is UB. However, till
GCC 12 it was accepted and std::convertible returned false.
This fails now for e.g. v8::internal::WasmArray. Use
std::disjunction and std::conjunction instead which are short-
circuiting, because std::is_base_of<T, T> is already true.

Bug: chromium:957519
Change-Id: Ia26643dbdf0fb00d5586c71ae6b18e8d0f3cf96e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4394663
Commit-Queue: Stephan Hartmann <[email protected]>
Reviewed-by: Clemens Backes <[email protected]>
Cr-Commit-Position: refs/heads/main@{#86904}

Author: stha09

src/codegen/tnode.h

@@ -270,8 +270,9 @@ using BuiltinPtr = Smi;
 template <class T, class U>
 struct is_subtype {
   static const bool value =
-      std::is_base_of<U, T>::value || (std::is_same<U, MaybeObject>::value &&
-                                       std::is_convertible<T, Object>::value);
+      std::disjunction<std::is_base_of<U, T>,
+                       std::conjunction<std::is_same<U, MaybeObject>,
+                                        std::is_convertible<T, Object>>>::value;
 };
 template <class T1, class T2, class U>
 struct is_subtype<UnionT<T1, T2>, U> {