}
	}
	return outGo, outC, outCXX, nil
}

// Make sure SWIG is new enough.
var (
	swigCheckOnce sync.Once
	swigCheck     error
)

func (b *Builder) swigDoVersionCheck() error {
	sh := b.BackgroundShell()
	out, err := sh.runOut(".", nil, "swig", "-version")
	if err != nil {
		return err
	}
	re := regexp.MustCompile(`[vV]ersion +(\d+)([.]\d+)?([.]\d+)?`)