GCC 4.9 introduces a newer C++ ABI version than your system libstdc++ has, so you need to tell the loader to use this newer version of the library by adding that path to
LD_LIBRARY_PATH. Unfortunately, I cannot tell you straight off where the libstdc++ so for your GCC 4.9 installation is located, as this depends on how you configured GCC. So you need something in the style of:
Note the actual path may be different (there might be some subdirectory hidden under there, like `x86_64-unknown-linux-gnu/4.9.0´ or similar).