Fix wheel building configuration in CI by installing libatomic1.

[reivilibre]

Without this, we get the following error when building for 32-bit i686 Linux:

Running before_all...
  
      + /opt/python/cp38-cp38/bin/python -c 'import sys, json, os; json.dump(os.environ.copy(), sys.stdout)'
      + sh -c 'curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain 1.82.0 -y --profile minimal'
  info: downloading installer
  warn: Not enforcing strong cipher suites for TLS, this is potentially less secure
  /tmp/tmp.KlFNNCWiwj/rustup-init: error while loading shared libraries: libatomic.so.1: cannot open shared object file: No such file or directory
                                                              ✕ 1.30s
Error: Command ['sh', '-c', 'curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain 1.82.0 -y --profile minimal'] failed with code 1. 

There may be other platforms where this is relevant, too. (libatomic provides software support for some atomic operations when not supported directly by hardware)

[devonh]

These changes look sane to me.
As long as all containers used to build wheels have libatomic1 available as a library, which I think is true.