Running cargo build gives errors like:
Process didn't exit successfully: `rustc - --crate-name - --crate-type dylib --crate-type bin --print=file-names` (status=101)
--- stderr
error: crate name cannot start with a hyphen: -
error: aborting due to previous error
The nightly before that latest one is 2015-02-22, which you can obtain/reobtain with the --date=2015-02-22 argument to rustup.sh, or via multirust default nightly-2015-02-22.
This was possibly issue #1342, which is apparently fixed in master, but seemingly not in time to get into that nightly.