Add Fuchsia as recognized host OS in uname.
Add Fuchsia as recognized host OS in uname.

tempbottle/coreutils,uutils/coreutils,keunwoo/coreutils,tempbottle/coreutils,Arcterus/coreutils,keunwoo/coreutils,uutils/coreutils,uutils/coreutils,Arcterus/coreutils