cmd/ld: trivial: fix unused parameter pedantry
cmd/ld: trivial: fix unused parameter pedantry

R=golang-dev, r, rsc
CC=golang-dev
https://codereview.appspot.com/11436043

tv42/old-go,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,apparentlymart/golang,pombredanne/go-deleteme,pombredanne/go-deleteme,apparentlymart/golang,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,apparentlymart/golang,tv42/old-go,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang