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

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