Fix: python bindings when building with PIE hardening

Fix: python bindings when building with PIE hardening

Work around a bug/limitation in python distutils where object files are
built with -fPIC appended after the CFLAGS but the final shared object
is linked with -shared before the LDFLAGS which can then be overriden by
hardening flags and result in an invalid build.

The work around is to append -shared to the LDFLAGS making sure it's not
overriden.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>