[llvm] [ADT] Reimplement operator==(StringRef (PR #91139)

[Jakub Kuderski via llvm-commits]

================
@@ -871,7 +871,11 @@ namespace llvm {
   /// @{
 
   inline bool operator==(StringRef LHS, StringRef RHS) {
-    return LHS.equals(RHS);
+    if (LHS.size() != RHS.size())
+      return 0;
+    if (LHS.empty())
+      return 1;
----------------
kuhar wrote:

```suggestion
      return true;
```

https://github.com/llvm/llvm-project/pull/91139