cmd/dist: set -Wuninitialized only when -O is also set. GCC on OS X 10.6 doesn't support -Wuninitialized without -O. Fixes issue 7492.
cmd/dist: set -Wuninitialized only when -O is also set.
GCC on OS X 10.6 doesn't support -Wuninitialized without -O.
Fixes issue 7492.

LGTM=iant
R=golang-codereviews, dave, iant
CC=golang-codereviews
https://codereview.appspot.com/72360045

apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang