chore(linux): setup.py install is deprecated.

[ermshiperete]

Running linux/keyman-config/build.sh install results in a warning:

/usr/lib/python3/dist-packages/setuptools/_distutils/cmd.py:66: SetuptoolsDeprecationWarning: setup.py install is deprecated.
15:53:09   !!
15:53:09   
15:53:09           ********************************************************************************
15:53:09           Please avoid running ``setup.py`` directly.
15:53:09           Instead, use pypa/build, pypa/installer or other
15:53:09           standards-based tools.
15:53:09   
15:53:09           See https://blog.ganssle.io/articles/2021/10/setup-py-deprecated.html for details.
15:53:09           ********************************************************************************
15:53:09   
15:53:09   !!
15:53:09     self.initialize_options()
15:53:09   /usr/lib/python3/dist-packages/setuptools/_distutils/cmd.py:66: EasyInstallDeprecationWarning: easy_install command is deprecated.
15:53:09   !!
15:53:09   
15:53:09           ********************************************************************************
15:53:09           Please avoid running ``setup.py`` and ``easy_install``.
15:53:09           Instead, use pypa/build, pypa/installer or other
15:53:09           standards-based tools.
15:53:09   
15:53:09           See https://github.com/pypa/setuptools/issues/917 for details.
15:53:09           ********************************************************************************
15:53:09   
15:53:09   !!
15:53:09     self.initialize_options()
15:53