build: disable cgo on Windows/amd64
build: disable cgo on Windows/amd64

Apparently it is broken.  Disable so that dashboard
will let us see other breakages on Windows.

R=golang-dev, bradfitz
CC=golang-dev
http://codereview.appspot.com/5477081

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