Patched commands ignore `setup.cfg` defined options

[althonos]

Hi there,
the setup.cfg file allows to define default values for arguments of setuptools / distutils commands. With the following file:

[build_rust]
inplace = true
release = true

simply running python setup.py build_rust will build all the extensions inplace and in release mode as expected.

Unfortunately, running python setup.py build or python setup.py build_ext does not. I suspect there's a step in the monkey-patching where the build_rust command is ran without having finalize_options called or something like that.