(resending publicly at Attila's suggestion)
I'm really happy to see this, because I've been working on something similar:https://github.com/akkartik/mu
It has a linux/ subdirectory analogous to Maru's `linux` platform that generates ELF binaries without needing any third-party tooling. The ELF binaries can run with just an OS kernel. It also has a 'baremetal' version at the top level that doesn't need an OS. (Though it does need linux/ to bootstrap itself.)
Most of it is a low-level statement-oriented language, but I've been starting to give it a very rudimentary, interpreted Lisp-based HLL. At first glance Maru seems like a really good candidate for a Mu port.