cmake: Define library suffix in case of 64 bits multilib archs in linux

Signed-off-by: Helio Chisisni de Castro <helio@kde.org>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
CMakeLists.txt: Fix python due undefined cmake variable

Signed-off-by: Helio Chissini de Castro <helio@kde.org>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>