cmd/dist: force line-buffering stdout/stderr on Unix         If stdout and stderr are indeed the same file (not a tty), which is         often the case, fully-buffered stdout will make it harder to see         progresses, for example, ./make.bash 2>&1 | tee log
cmd/dist: force line-buffering stdout/stderr on Unix
        If stdout and stderr are indeed the same file (not a tty), which is
        often the case, fully-buffered stdout will make it harder to see
        progresses, for example, ./make.bash 2>&1 | tee log

R=r, rsc
CC=golang-dev
http://codereview.appspot.com/5700070

wesolows/golang,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang,wesolows/golang-old,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old