Fix broken fuzz test in test.yaml GHA for macos

[rrybarczyk]

GitHub actions in test.yaml does not pass for macos os.

Logic to skip macos and just run ubuntu is added here in #241.

Failing action logs for macos is found here.

I wonder if changing the toolchain to nightly in the test.yaml caused this problem?

[xraid]

docs for affinity says not tested on osx, but there is a PR for MacOS in repo :
affinity
affinity/pull/8

while core_affinity is said to work on
x86_64-apple-darwin
i686-apple-darwin

also cpu-affinity has support for MacOS

i guess GHA is pulling in affinity from fuzz in repo that ask for crate num_cpu ?

[xraid]

maybe look at rayon-rs

[GitGab19]

Closing this as stale