python path: work around a bug in a Fedora patch

The Fedora python package patches the get_python_lib() function in
distutils.sysconfig, breaking its API by returning different values,
depending on plat_specific, even if prefix is given.

See https://bugzilla.redhat.com/show_bug.cgi?id=1076293.

Work around that by checking for the different path and adding it to the
path as well.