rule/platform.go
func (p Platform) String() string {
	switch {
	case p.OS != "" && p.Arch != "":
		return p.OS + "_" + p.Arch
	case p.OS != "":
		return p.OS
	case p.Arch != "":
		return p.Arch
	default:
		return ""
	}
}
func (p Platform) String() string {
	switch {
	case p.OS != "" && p.Arch != "":
		return p.OS + "_" + p.Arch
	case p.OS != "":
		return p.OS
	case p.Arch != "":
		return p.Arch
	default:
		return ""
	}
}
// String returns OS, Arch, or "OS_Arch" if both are set. This must match
// the names of config_setting rules in @io_bazel_rules_go//go/platform.