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

[Evgenii Kudriashov via llvm-commits]

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@@ -16,8 +16,11 @@ namespace coff {
 using namespace object;
 
 void Object::addSymbols(ArrayRef<Symbol> NewSymbols) {
+  size_t RawIndex = 0;
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e-kud wrote:

@mstorsjo I've noticed that this approach is error-prone as if `addSymbols` invoked twice, symbols will have duplicated `OriginalRawIndex` (It doesn't happen now). Looks like we should have this variable as a class member.

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