Fix possible memory leak

Author: valeriyvan

lib/IRGen/IRGen.cpp

@@ -1205,9 +1205,10 @@ swift::irgen::createIRGenModule(SILModule *SILMod, StringRef OutputFilename,
                                 IRGenOptions &Opts) {
   IRGenerator *irgen = new IRGenerator(Opts, *SILMod);
   auto targetMachine = irgen->createTargetMachine();
-  if (!targetMachine)
+  if (!targetMachine) {
+    delete irgen;
     return std::make_pair(nullptr, nullptr);
-
+  }
   // Create the IR emitter.
   IRGenModule *IGM = new IRGenModule(
       *irgen, std::move(targetMachine), nullptr, "", OutputFilename,