> I'm not sure how -- or if -- Rust will fix this issue.

We're addressing this as we speak! We've split out the stdlib into many constituent libraries that depend on each other, and then just made the stdlib a convenient facade for these libraries. After opting out of the stdlib, you can then opt into any of the "core" libraries as you like, a la carte. Many of these smaller libs don't rely on the runtime (they don't depend on librustrt) nor do they rely on allocation at all (liballoc), and can thus be used in a freestanding environment. See the other comment in this thread for more details:

https://news.ycombinator.com/item?id=7883451