Python extension module should be installed into arch-dependent directory

Currently Python extension module installs in '/usr/lib/python3.X/site-packages' but proper place is '/usr/lib64/python3.X/site-packages' on 64bit architectures (e.g. x86_64) and '/usr/lib/python3.X/site-packages on 32bit', see https://docs.fedoraproject.org/en-US/packaging-guidelines/Python/.

Why this was made in early days documented in Compiz:

  # We must build the python module using CMake instead of distutils.
  #
  # The only way in which the python module can be built using distutils
  # is by using add_custom_command to "generate" it into existence.
  # Unfortunately this has drawbacks. Namely, it is not possible for
  # add_custom_command to depend on library targets. Because of that, there's
  # no way that we can guarantee that libcompizconfig.so will be linked
  # before compizconfig.so (which is required). The best that we can do
  # there is to use add_custom_target, and make that target depend on the
  # file,

but seems like this is not an issue anymore in new Cmake versions:

  > Changed in version 3.16: A target-level dependency is added if any dependency is a byproduct of a target or any of its build events in the same directory to ensure the byproducts will be available before this target is built.

https://cmake.org/cmake/help/latest/command/add_dependencies.html#command:add_dependencies