package/libselinux: fix build with gcc 4.8

Fix build failure with gcc 4.8 which is raised since bump to version 3.2
in commit b7ff4751

Fixes:
 - http://autobuild.buildroot.org/results/37eb0952a763256fbf6ef3c668f6c95fbdf2dd35



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Tested-by: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>