Update ELFObjectWriter::reset() following r238073.

llvm-svn: 240218
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 234c350..c9df8fc 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -144,6 +144,7 @@
       Renames.clear();
       Relocations.clear();
       StrTabBuilder.clear();
+      SymtabShndxSectionIndex = 0;
       SectionTable.clear();
       MCObjectWriter::reset();
     }