ARM Builds

[AusIV]

Now that AWS has A1 instances, it would be neat if we could include those in our docker host cluster. That would require being able to create multiarch docker images, which would require cross-compiling to ARM.

Normally, cross compilation in Go is pretty easy; it's just a matter of passing GOARCH at build time. However OpenRelay has some C dependencies that don't work with GOARCH. I've been able to get a build up using xgo (https://github.com/karalabe/xgo), but integrating that into our build process seems cumbersome and likely slow.