About a week ago it was finally merged into Rust master branch which is really great as it is much easier to work on smaller changes now.
Here are instructions on how to build it. So far there is no official iOS buildbot and therefore it might broke at any moment, in this case I recommend to use a original fork which could be considered a “stable” branch, tested to compile and work both on device and simulator. It might lag a bit from the master but not that much.
There is still one issue in LLVM which sometimes crashes compilation process. Patch was submitted but considering previous experience I wouldn’t expect it to be landed in less than a month.
I’ve started work on Arm64 port but it definitely will take much more time considering I have no test device.