Force GCC to notify about undefined references in shared libraries

-Wl,--no-undefined linker option can be used when building shared library, undefined symbols will be shown as linker errors.

g++ -shared -Wl,-soname,libmylib.so.5 -Wl,--no-undefined \
    -o libmylib.so.1.1 mylib.o -lthirdpartylib