Unable to override Rustup toolchain for custom build of iOS Toolchain

I am creating my own toolchain with my build of Rust. I need this to cross compile with iOS architectures. When trying to set the default toolchain or override the current directory's toolchain, I'm getting an error regarding the name of my toolchain. These are the steps I took to create this new toolchain:

  1. Create Rustup Toolchain
    $ rustup toolchain link ios $HOME/rustc-ios

  2. Override current directory toolchain rustup override set ios
    $ rustup show Default host: x86_64-apple-darwin error: toolchain 'ios' does not support components info: caused by: invalid toolchain name: 'ios'

I've tried other names that conform to the toolchain naming conventions, but to of no avail:

$ rustup toolchain link stable-2016-07-19-x86_64-apple-ios $HOME/rustc-ios error: invalid custom toolchain name: 'stable-2016-07-19-x86_64-apple-ios'
$ rustup toolchain link stable-x86_64-apple-ios $HOME/rustc-ios error: invalid custom toolchain name: 'stable-x86_64-apple-ios'
$ rustup toolchain link x86_64-apple-ios $HOME/rustc-ios

Here's the question post on StackOverflow:
http://stackoverflow.com/questions/38466493/unable-to-override-rustup-toolchain-for-custom-build-of-ios-toolchain