[clang] [clang][bytecode] Avoid crash in constexpr wcslen on invalid argument… (PR #177891)

[Timm Baeder via cfe-commits]

================
@@ -367,10 +367,14 @@ static bool interp__builtin_strlen(InterpState &S, CodePtr OpPC,
   unsigned ElemSize = StrPtr.getFieldDesc()->getElemSize();
 
   if (ID == Builtin::BI__builtin_wcslen || ID == Builtin::BIwcslen) {
-    [[maybe_unused]] const ASTContext &AC = S.getASTContext();
-    assert(ElemSize == AC.getTypeSizeInChars(AC.getWCharType()).getQuantity());
+    const ASTContext &AC = S.getASTContext();
+    unsigned WCharSize = AC.getTypeSizeInChars(AC.getWCharType()).getQuantity();
+    if (ElemSize != WCharSize) {
+      return false;
+    }
----------------
tbaederr wrote:

```suggestion
    if (ElemSize != WCharSize)
      return false;
```

https://github.com/llvm/llvm-project/pull/177891