Undefined reference to boost::system::detail::system_category_instance that gets fixed when switching from C++14 to C++11

I am trying to build my C++ application that uses boost 1.68.0. On trying to build it using cmake followed by make, I get the following linking errors,

/usr/local/bin/g++   -Wall -Wextra -g3 -std=c++14 -Wl,-rpath=/usr/local/lib -L/usr/local/lib    CMakeFiles/Supervisor.dir/HeartbeatManager.cpp.o CMakeFiles/Supervisor.dir/JobReceiver.cpp.o CMakeFiles/Supervisor.dir/ResultSender.cpp.o CMakeFiles/Supervisor.dir/Supervisor.cpp.o CMakeFiles/Supervisor.dir/Process.cpp.o  -o Supervisor -rdynamic -lpthread -lboost_system-mt 
CMakeFiles/Supervisor.dir/HeartbeatManager.cpp.o: In function `boost::system::system_category()':
/usr/local/include/boost/system/error_code.hpp:473: undefined reference to `boost::system::detail::system_category_instance'

On switching the -std=c++14 flag with -std=c++11, the error disappears. I got the idea from this answer. I do not know why that fixes it? Now in my project I cannot use -std=c++11 flag instead of the -std=c++14 flag.