builder/vmware: clarify guestiphack error message [GH-639]

builder/vmware/driver_esx5.go

@@ -314,7 +314,8 @@ func (d *ESX5Driver) checkGuestIPHackEnabled() error {
 	}
 
 	if record["IntValue"] != "1" {
-		return errors.New("GuestIPHack is required, enable with:\n" +
+		return errors.New(
+			"GuestIPHack is required, enable by running this on the ESX machine:\n" +
 			"esxcli system settings advanced set -o /Net/GuestIPHack -i 1")
 	}