Use reference to iterate through string table instead of copying.

[ecbeckmann]

Summary

just a quick patch

llvm/trunk/lib/Object/WindowsResource.cpp

for (auto DataNodes : DataEntriesTreeOrder) {
     CurrentOffset += sizeof(llvm::object::coff_resource_data_entry);
     CurrentRelativeOffset += sizeof(llvm::object::coff_resource_data_entry);
   }
 }
 
 void WindowsResourceCOFFWriter::writeDirectoryStringTable() {
   // Now write the directory string table for .rsrc$01
   uint32_t TotalStringTableSize = 0;
-  for (auto String : StringTable) {
+  for (auto &String : StringTable) {
     uint16_t Length = String.size();
     support::endian::write16le(BufferStart + CurrentOffset, Length);
     CurrentOffset += sizeof(uint16_t);
     auto *Start = reinterpret_cast<UTF16 *>(BufferStart + CurrentOffset);
     std::copy(String.begin(), String.end(), Start);
     CurrentOffset += Length * sizeof(UTF16);
     TotalStringTableSize += Length * sizeof(UTF16) + sizeof(uint16_t);
   }