MC/COFF: Correctly emit the size of an empty string table.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144111 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/WinCOFFObjectWriter.cpp

@@ -281,6 +281,7 @@ StringTable::StringTable() {
   // The string table data begins with the length of the entire string table
   // including the length header. Allocate space for this header.
   Data.resize(4);
+  update_length();
 }
 
 size_t StringTable::size() const {