[Orc] Two small fixes in TPCDynamicLibrarySearchGenerator

[sgraenitz]

Summary

Two details we missed in D90132:
There is one result per lookup symbol, so we have to advance the result iterator no matter whether it's NULL or not.
MissingSymbols variable is unused.

[sgraenitz]

Friendly ping. @lhames Can you confirm this fix? I couldn't find a test for this piece of code.

[lhames]

LGTM -- Nice catch, thanks Stefan!

llvm/lib/ExecutionEngine/Orc/TPCDynamicLibrarySearchGenerator.cpp

Error TPCDynamicLibrarySearchGenerator::tryToGenerate(
   auto Result = TPC.lookupSymbols(Request);
   if (!Result)
     return Result.takeError();
 
   assert(Result->size() == 1 && "Results for more than one library returned");
   assert(Result->front().size() == LookupSymbols.size() &&
          "Result has incorrect number of elements");
 
-  SymbolNameVector MissingSymbols;
   auto ResultI = Result->front().begin();
-  for (auto &KV : LookupSymbols)
+  for (auto &KV : LookupSymbols) {
     if (*ResultI)
       NewSymbols[KV.first] =
-          JITEvaluatedSymbol(*ResultI++, JITSymbolFlags::Exported);
+          JITEvaluatedSymbol(*ResultI, JITSymbolFlags::Exported);
+    ResultI++;
+  }
 
   // If there were no resolved symbols bail out.
   if (NewSymbols.empty())
     return Error::success();
 
   // Define resolved symbols.
   return JD.define(absoluteSymbols(std::move(NewSymbols)));
 }
 
 } // end namespace orc
 } // end namespace llvm