[clang] [BoundsSafety][Sema] Allow `sized_by`/`sized_by_or_null` on pointers to structs with a flexible array member (PR #209603)

[Dan Liew via cfe-commits]

================
@@ -152,7 +152,8 @@ bool Sema::CheckCountedByAttrOnField(FieldDecl *FD, Expr *E, bool CountInBytes,
     InvalidTypeKind = CountedByInvalidPointeeTypeKind::SIZELESS;
   } else if (PointeeTy->isFunctionType()) {
     InvalidTypeKind = CountedByInvalidPointeeTypeKind::FUNCTION;
-  } else if (PointeeTy->isStructureTypeWithFlexibleArrayMember()) {
+  } else if (PointeeTy->isStructureTypeWithFlexibleArrayMember() &&
+             !CountInBytes) {
----------------
delcypher wrote:

Followup here: https://github.com/llvm/llvm-project/pull/209713

https://github.com/llvm/llvm-project/pull/209603