Created by: dzhwinter

when it compile the stringpiece, compiler goes in wrong way of using the gcc instead of g++.

Undefined symbols for architecture x86_64:
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::operator<<<char, std::__1::char_traits<char>, std::__1::allocator<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)", referenced
 from:
      paddle::operator<<(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, paddle::StringPiece) in libstringpiece.a(stringpiece.cc.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [paddle/strings/stringpiece_test] Error 1
make[1]: *** [paddle/strings/CMakeFiles/stringpiece_test.dir/all] Error 2
make: *** [all] Error 2