[llvm] Add clang::lifetimebound annotation to ArrayRef constructors. (PR #113547)

[Haojian Wu via llvm-commits]

================
@@ -113,7 +115,8 @@ namespace llvm {
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Winit-list-lifetime"
 #endif
-    constexpr /*implicit*/ ArrayRef(const std::initializer_list<T> &Vec)
+    constexpr /*implicit*/ ArrayRef(
+        const std::initializer_list<T> &Vec LLVM_LIFETIME_BOUND)
----------------
hokein wrote:

We have a tricky case with an empty initializer_list:

```
ArrayRef<int> ref({}); 
```

clang still diagnoses it as dangling reference, but the code doesn't have any dangling references. I think it is ok, this is similar to `make_unique<pointer>(nullptr).get()` case (https://github.com/llvm/llvm-project/issues/97471).

https://github.com/llvm/llvm-project/pull/113547