fix compile failure: legacy cuserid needs to define feature test
fix compile failure: legacy cuserid needs to define feature test

chardi/musl,rofl0r/musl-old,davidlazar/musl,davidlazar/musl,rofl0r/musl-old,chardi/musl,chardi/musl,chneukirchen/musl-chris2,chneukirchen/musl-chris2