patch from njk: make x86_64 __uniclone branchless.
patch from njk: make x86_64 __uniclone branchless.

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