I just noticed that rustc_codegen_gcc has been accepted into the mainline Rust compiler, or at least the nightly builds.

https://github.com/rust-lang/rust/pull/151156

This means that you will be able to use either GCC or LLVM to build your Rust code with rustc (the main Rust compiler). That means you can compile your Rust for any platform that GCC supports.

This only addresses the first point in the blog post (architecture support) but it is an interesting development.