package/faifa: fix musl build

Fixes
http://autobuild.buildroot.net/results/dc6/dc6e4d7327d2031ef921cccd814605dec73a0f9c/
http://autobuild.buildroot.net/results/868/868642325dbcd581373eaa9e1ef900f8a27f9121/


and others

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>