[llvm] [llvm-objcopy][COFF] Update WinCFGuard section contents after stripping (PR #153322)

[Evgenii Kudriashov via llvm-commits]

================
@@ -92,6 +93,63 @@ Error COFFWriter::finalizeSymbolContents() {
   return Error::success();
 }
 
+Error COFFWriter::finalizeCFGuardContents() {
+  DenseMap<size_t, size_t> SymIdMap;
+  bool NeedUpdate = false;
+  for (Symbol &Sym : Obj.getMutableSymbols()) {
+    NeedUpdate |= Sym.OriginalRawIndex == Sym.RawIndex;
+    SymIdMap[Sym.OriginalRawIndex] = Sym.RawIndex;
+  }
+
+  if (!NeedUpdate)
+    return Error::success();
+
+  for (auto &Sym : Obj.getMutableSymbols()) {
+    if (Sym.Name != ".gljmp$y" && Sym.Name != ".giats$y" &&
+        Sym.Name != ".gfids$y")
+      continue;
+
+    auto Sec = find_if(Obj.getMutableSections(),
+                       [&Sym](Section &S) { return S.Name == Sym.Name; });
+
+    if (Sec == Obj.getMutableSections().end() ||
+        Sec->UniqueId != Sym.TargetSectionId)
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e-kud wrote:

Currently we match symbols using `Sec.UniqueId` in a map formed from `Sym.TargetSectionId`. Should be resolved.

https://github.com/llvm/llvm-project/pull/153322