cmd/gc: silence clang warning
cmd/gc: silence clang warning

This code is only built when you run 'make' in cmd/gc,
not in all.bash.

R=golang-dev, jsing, iant
CC=golang-dev
https://codereview.appspot.com/19160043

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