[lld] [LLD] [COFF] Fix handling of comdat .drectve sections (PR #68116)

[Alexandre Ganea via llvm-commits]

================
@@ -660,10 +660,15 @@ std::optional<Symbol *> ObjFile::createDefined(
 
     if (prevailing) {
       SectionChunk *c = readSection(sectionNumber, def, getName());
-      sparseChunks[sectionNumber] = c;
-      c->sym = cast<DefinedRegular>(leader);
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aganea wrote:

nit: you could also insert at L664:
```
      if (!c)
        return nullptr;
```

https://github.com/llvm/llvm-project/pull/68116