Undefined symbols for architecture x86_64:
  "google::FlagRegisterer::FlagRegisterer<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >(char const*, char const*, char const*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*)", referenced from:
      ___cxx_global_var_init.30 in libReact.a(logging.o)
      ___cxx_global_var_init.73 in libReact.a(logging.o)
      ___cxx_global_var_init.80 in libReact.a(logging.o)
      ___cxx_global_var_init.87 in libReact.a(logging.o)
      ___cxx_global_var_init.108 in libReact.a(logging.o)
      ___cxx_global_var_init.10 in libReact.a(vlog_is_on.o)
  "google::FlagRegisterer::FlagRegisterer<bool>(char const*, char const*, char const*, bool*, bool*)", referenced from:
      ___cxx_global_var_init.5 in libReact.a(logging.o)
      ___cxx_global_var_init.14 in libReact.a(logging.o)
      ___cxx_global_var_init.21 in libReact.a(logging.o)
      ___cxx_global_var_init.39 in libReact.a(logging.o)
      ___cxx_global_var_init.103 in libReact.a(logging.o)
      ___cxx_global_var_init.4 in libReact.a(utilities.o)
  "google::FlagRegisterer::FlagRegisterer<int>(char const*, char const*, char const*, int*, int*)", referenced from:
      ___cxx_global_var_init.24 in libReact.a(logging.o)
      ___cxx_global_var_init.46 in libReact.a(logging.o)
      ___cxx_global_var_init.53 in libReact.a(logging.o)
      ___cxx_global_var_init.60 in libReact.a(logging.o)
      ___cxx_global_var_init.67 in libReact.a(logging.o)
      ___cxx_global_var_init.96 in libReact.a(logging.o)
      ___cxx_global_var_init.3 in libReact.a(vlog_is_on.o)
      ...
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)