[llvm] Use MapVector to fix lld thinLTO bep issue. (PR #117551)

[Vitaly Buka via llvm-commits]

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@@ -28,11 +29,11 @@ class RecordStreamer : public MCStreamer {
 
 private:
   const Module &M;
-  StringMap<State> Symbols;
+  MapVector<StringRef, State> Symbols;
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vitalybuka wrote:

I would not expect nondeterminism from Symbols
Order in hash table should be determined character in StringRefs and order they inserted.
Should be the same all the time?

https://github.com/llvm/llvm-project/pull/117551