[lld] [lld-macho] Fix category merging category map non-determinism (PR #91159)

[Kyungwoo Lee via llvm-commits]

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@@ -341,10 +341,13 @@ class ObjcCategoryMerger {
     ConcatInputSection *catListIsec;
     ConcatInputSection *catBodyIsec;
     uint32_t offCatListIsec = 0;
+    uint32_t inputIndex = 0;
 
     bool wasMerged = false;
   };
 
+  typedef std::vector<InfoInputCategory> CategoryGroup;
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kyulee-com wrote:

```suggestion
using CategoryGroup = std::vector<InfoInputCategory>;
```

https://github.com/llvm/llvm-project/pull/91159