Rust is designed to compile fine without any borrow checking (it reduces it to the C level of safety, but valid programs generate valid code).
GCC will compile itself without a borrow checker. Then it will compile the existing borrow checker written in Rust, and then recompile itself with borrow checking.
Did they announce a change of plans? Their website just says that they have no plans for a borrow checker (i.e. it's not required to actually implement rust).
From the website for the project:
> There are no immediate plans for a borrow checker as this is not required to compile rust code and is the last pass in the RustC compiler. This can be handled as a separate project when we get to that point.
Link here: https://rust-gcc.github.io/