When using [this custom target](https://github.com/thepowersgang/wince-books/blob/master/armv4-mingw32ce.json) to compile libcore (and I'd assume any other crate), rustc ICEs on an unwrap in the above named function. This unwrap at [diagnostic.rs:88](https://github.com/rust-lang/rust/blob/master/src/librustc_codegen_llvm/llvm/diagnostic.rs#L88) seems to be only able to fail if there's a null reference in LLVM (or in the rustc shim)