cmd/dist: add missing Native Client bits
cmd/dist: add missing Native Client bits

Some parts of CL 15400047 didn't survive the merge.

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://codereview.appspot.com/69870044

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang