title: reading "--plat-name" argument in setup.py
body: <p>The setuptools <code>bdist_wheel</code>/<code>bdist_egg</code> commands have a <code>--plat-name</code> argument that allows for overriding the host platform name.  This value gets tacked onto the name of the resulting file, e.g., <code>mypackage-1.2.3-py2.py3-none-manylinux1_x86_64.whl</code>.</p>
  
  <p>How can I read this value in <code>setup.py</code>?  Note I'm <em>not</em> asking for the host platform the script is running on, e.g., <code>platform.system()</code>.  I want the platform name that setuptools is using.</p>