Split Finish into Finish and FinishImpl to have a common place to do end of

file error checking. Use that to error on an unfinished cfi_startproc.

The error is not nice, but is already better than a segmentation fault.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147717 91177308-0d34-0410-b5e6-96231b3b80d8

tools/lto/LTOModule.cpp

@@ -603,7 +603,7 @@ namespace {
         if (Inst.getOperand(i).isExpr())
           AddValueSymbols(Inst.getOperand(i).getExpr());
     }
-    virtual void Finish() {}
+    virtual void FinishImpl() {}
   };
 }