[clang] [clang] Implement `__builtin_is_implicit_lifetime()` (PR #101807)

[Timm Baeder via cfe-commits]

================
@@ -5637,6 +5638,27 @@ static bool EvaluateUnaryTypeTrait(Sema &Self, TypeTrait UTT,
     return false;
   case UTT_IsTriviallyEqualityComparable:
     return isTriviallyEqualityComparableType(Self, T, KeyLoc);
+  case UTT_IsImplicitLifetime: {
+    DiagnoseVLAInCXXTypeTrait(Self, TInfo,
+                              tok::kw___builtin_is_implicit_lifetime);
+    QualType UnqualT = T->getCanonicalTypeUnqualified();
+    if (UnqualT->isScalarType())
+      return true;
+    if (UnqualT->isArrayType())
+      return true;
+
+    CXXRecordDecl *RD = UnqualT->getAsCXXRecordDecl();
----------------
tbaederr wrote:

```suggestion
    const CXXRecordDecl *RD = UnqualT->getAsCXXRecordDecl();
```

https://github.com/llvm/llvm-project/pull/101807