libc: add goos, goarch, goroot.  fixes build
libc: add goos, goarch, goroot.  fixes build

TBR=r
CC=golang-dev
http://codereview.appspot.com/190059
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go