While 'nix build .#jj' worked fine, it seems like 'nix develop .' did *not* work
fine, due to a bug in upstream nixpkgs when libgcc_s was linked against the MSRV
(1.64.0). A simple update seems to have fixed that.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
Change-Id: Iwqryoplqxzyxwymlsktxnqoqrwvrryln
This gets used by `nix develop`, or automatically by `direnv` if you have it
installed.
The binary versions are pinned to the versions recommended by `contributing.md`.
```
>> cargo --version
cargo 1.60.0 (d1fd9fe 2022-03-01)
>> rustc --version
rustc 1.60.0 (7737e0b5c 2022-04-04)
>> cargo fmt --version
rustfmt 1.5.1-nightly (3984bc5 2023-01-17)
>> cargo clippy --version
clippy 0.1.60 (7737e0b 2022-04-04)
```
