cmd/cgo: simpler fix for issue 6506. Replaces CL 14682044. Fixes issue 6506.
cmd/cgo: simpler fix for issue 6506.
Replaces CL 14682044.
Fixes issue 6506.

R=rsc, iant, dave
CC=golang-dev
https://codereview.appspot.com/14717043

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