Use a specific nightly toolchain as a workaround for building puzzlefs

[ariel-miculas]

Starting from nightly-2022-08-03, puzzlefs no longer builds because of the following error: error[E0407]: method backtrace is not a member of trait std::error::Error --> format/src/error.rs:13:10	13	#[derive(Error)]	^^^^^ not a member of trait std::error::Error

= note: this error originates in the derive macro Error (in Nightly builds, run with -Z macro-backtrace for more info)

Use nightly-2022-08-02 for now for lack of a better solution.

Signed-off-by: Ariel Miculas amiculas@cisco.com

[hallyn]

Thanks that fixed it for me.

[hallyn]

Odd, while this fixed the build for me locally, it failed in github actions:

https://github.com/anuvu/puzzlefs/actions/runs/3221351471

Also noteworthy that actions appear to be running on merges into master, but not on prs...