package/luv: fix build with gcc 4.8

Fixes:
 - http://autobuild.buildroot.org/results/83b34e606b128546da8a70836d039090e334a1ec



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[yann.morin.1998@free.fr: mark patch accepted upstream]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>