python: fix build error for missing library_path in setup.py
python: fix build error for missing library_path in setup.py

Patch obtained from gentoo package.

https://bugs.gentoo.org/show_bug.cgi?id=477110
https://bugs.gentoo.org/show_bug.cgi?id=490584

Signed-off-by: Thomas Haller <16e26612e4159990a6b3691e92592e691ff74132@redhat.com>

cyclops8456/libnl3,tgraf/libnl,mshirley/libnl,kolyshkin/libnl,houstar/libnl,honsys/libnl,baloo/libnl,thom311/libnl,UnicronNL/libnl3,honsys/libnl,tklauser/libnl,congwang/libnl,cyclops8456/libnl3,houstar/libnl,congwang/libnl,kolyshkin/libnl,cfriedt/libnl,HolyShitMan/libnl-1,kolyshkin/libnl,claudelee/libnl,HolyShitMan/libnl-1,UnicronNL/libnl3,UnicronNL/libnl3,congwang/libnl,thom311/libnl,mshirley/libnl,houstar/libnl,claudelee/libnl,dsahern/libnl,tgraf/libnl,baloo/libnl,UnicronNL/libnl3,HolyShitMan/libnl-1,honsys/libnl,kolyshkin/libnl,greearb/libnl-ct,vyos/libnl3,greearb/libnl-ct,baloo/libnl,dsahern/libnl,houstar/libnl,thom311/libnl,claudelee/libnl,greearb/libnl-ct,cfriedt/libnl,tklauser/libnl,congwang/libnl,mshirley/libnl,HolyShitMan/libnl-1,baloo/libnl,cyclops8456/libnl3,vyos/libnl3,tgraf/libnl,cfriedt/libnl,vyos/libnl3,honsys/libnl,dsahern/libnl,vyos/libnl3,tklauser/libnl,tgraf/libnl,claudelee/libnl,mshirley/libnl,cfriedt/libnl,dsahern/libnl,cyclops8456/libnl3,tklauser/libnl