net: LookupAddr doesn't work with literal IPv6 address w/ zone identifier when GODEBUG=netdns=cgo

[mikioh]

For example, on a node which keeps "fe80::1%lo0 localhost" line in /etc/hosts,

package main

import (
    "fmt"
    "net"
)

func main() {
    ptr, err := net.LookupAddr("fe80::1%lo0")
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(ptr)
}

results in

$ GODEBUG=netdns=cgo go run x.go 
lookup fe80::1%lo0: invalid address

$ GODEBUG=netdns=go go run x.go 
[localhost]

[gopherbot]

CL https://golang.org/cl/17215 mentions this issue.