-dynamic-link option added to link .so libs instead of static

Added by @pyalex:

"dynamic-link" (false by default) that changes flags used on linking stage (passed to ld).

When this flag is enabled instead of linking to python (via -l python3.x) we will use flags similar to what python itself uses during building extensions (see distutils.sysconfig.get_config_var("LDSHARED")). This allows packing the resulting .so / .dylib file into python package and distribute it via PyPi.

This has been already tested during publishing feast python package.