All,

I am happy to share a tool for developing and testing 64-bit ARM software on a x86_64 kernel/hardware.

This alternative, vArch, implements run-time user-mode translation of aarch64 to x86_64 ISA and one should notice considerably faster development cycles compare to the various
emulation tools. vArch is not suitable for kernel development. 

vArch itself is closed source but it is free for non-commercial use (e.g. similarly to Oracle JDK terms of use). In a nutshell, you can't redistribute vArch, but you are free to use any output
vArch generates as you wish. Specifically, any binaries generated by running the native ARM64 gcc under vArch can be redistributed freely, including for commercial use.

You can read all about it here: http://vArch.stratoscale.com

To get one going, the downloads page includes a VM that demos the stage4 aarch64 rootfs binaries booting under a x86_64 kernel using vArch.

Enjoy!

Best,
Dan.