Add arm64 support for terraform binary download

[pat-s]

Tested via a custom image.

The only issue I encountered is that the footer version was reported as "unknown" but that might be due to other changes in the image building process of mine and unrelated to this one.

Not sure if the solution is elegant, I am a beginner in GO and was just happy to get it working. Feel free to tweak to your liking!

#311

[leg100]

Thanks, I'll review this when I get some time tomorrow.

[leg100]

Hi @pat-s, I've had a look and I think you can make it simpler:

func (d *terraformDownloader) src(version string) string {
	return (&url.URL{
		Scheme: "https",
		Host:   d.host,
		Path: path.Join(
			"terraform",
			version,
			fmt.Sprintf("terraform_%s_%s_%s.zip", version, runtime.GOOS, runtime.GOARCH)),
	}).String()
}

Run go mod tidy after you've made the change to remove the requirement on shirou/gopsutil.

[pat-s]

Ahh interesting to see how little changes are required given that runtime contains all required information already...