Undefined symbols when building Poco for iPhone Simulator

I am having these link errors when building an Xcode 6.1.1 project for Simulator that links with Poco 1.6.0. OSX is 10.10.1 Yosemite.

Undefined symbols for architecture x86_64:
  "_opendir$INODE64", referenced from:
      Poco::DirectoryIteratorImpl::DirectoryIteratorImpl(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in libPocoFoundation.a(DirectoryIterator.o)
  "_readdir$INODE64", referenced from:
      Poco::DirectoryIteratorImpl::next() in libPocoFoundation.a(DirectoryIterator.o)
ld: symbol(s) not found for architecture x86_64

Questions:

1. Why is x86_64 architecture needed for the simulator?


2. Why can't these symbols be resolved?

Thanks in advance.