title: How to change build directory in setuptools
body: <p>I have a repo that I'm trying to modify to be deployable as a python package.
  Unfortunately, the root of the repository has a file named <code>BUILD</code> that cannot be changed due to existing CI integrations. As a result, when I attempt to <code>pip install</code> or <code>python setup.py bdist_wheel</code> or any other permutation of using <code>setuptools</code> it fails because it cannot create a <code>build/</code> directory.</p>
  <p>How can I change that build directory to be <code>_build/</code> or something non-conflicting?</p>
  <p>I've tried several things like <code>python setup.py build -b _build</code> which works for the build step in isolation, but I can't find an equivalent command line argument or <code>setup.py</code> option that will let me change it for all of the subcommands of <code>bdist_wheel</code>. There seem to be a lot of moving pieces that expect to be able to create a <code>build</code> directory at some point or reference it, and I haven't been able to track them all down.</p>