cmd/gc: fix build
cmd/gc: fix build

LGTM=minux.ma
R=rsc, minux.ma
CC=golang-codereviews
https://codereview.appspot.com/84260043

rdp/rogerpack2005-golang,bryanxu/go-zh,webfd/go-zh,bryanxu/go-zh,d0f/go-zh,bryanxu/go-zh,bryanxu/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,rdp/rogerpack2005-golang,d0f/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,webfd/go-zh,webfd/go-zh,bryanxu/go-zh,bryanxu/go-zh,rdp/rogerpack2005-golang,webfd/go-zh,d0f/go-zh,d0f/go-zh,rdp/rogerpack2005-golang,webfd/go-zh,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,webfd/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,d0f/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc