Fix conditional compilation of portable-atomic

[jayvdb]

Fix for #262

Caused by #233

c.f. https://doc.rust-lang.org/reference/conditional-compilation.html#r-cfg.target_has_atomic.general

[djc]

Is there something we could do in CI to catch this?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.88%. Comparing base (d7575cc) to head (0d3a8dd).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #264   +/-   ##
=======================================
  Coverage   80.88%   80.88%           
=======================================
  Files           6        6           
  Lines         633      633           
=======================================
  Hits          512      512           
  Misses        121      121           

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[jayvdb]

Use cargo-nextest to run the tests?

[djc]

Use cargo-nextest to run the tests?

I don't really want to pull that extra complexity into CI.