Consider naming the binary artifacts so they are easier to download

[coryan]

It would be nice if I could automatically download the right artifact for my current system using something like:

curl -sSL https://github.com/bazelbuild/buildtools/releases/download/5.1.0/buildifier-linux-$(uname -m)

But I cannot, because the artifact names do not match the output from uname -m (or uname with any other option). Maybe you can recommend a different way to automate this, or maybe consider renaming the artifacts so they match the output from the standard Linux tools?

[larsrc-google]

@vladmos Are these names (arm64, amd64) chosen arbitrarily or to match some other usage? amd64 seems particularly odd.