title: How to add platform-specific package data in setup.py?
body: <p>I would need to deploy platform-specific package data in the wheels built with setup.py</p>
  <p>For a bit of background, I am trying to create Python bindings for a certain library using pre-built binaries and ctypesgen.
  I have a data tree with platform-specific subdirectories that contain a bindings file and a binary each:</p>
  <pre><code>data/
      macos-arm64/
          _bindings.py
          binary.dylib
      linux-x64/
          _bindings.py
          binary.so
      windows-x64/
          _bindings.py
          binary.dll
      ...
  </code></pre>
  <p>And I have a source tree:</p>
  <pre><code>src/
      package_name/
          __init__.py
          __main__.py
          ...
  </code></pre>
  <p><strong>Question:</strong> How can I build platform-specific packages that only contain the one corresponding binary and bindings?</p>
  <p>The final directory tree as deployed to the end-user should structurally look like this:</p>
  <pre><code>package_name/
      __init__.py
      __main__.py
      _bindings.py
      binary.xyz
      ...
  </code></pre>