buildroot

python: remove *.pyo files

Even though we disable the build of .pyo files in the interpreter,
nothing prevents other packages to install them. Since we only want to
keep either .py or .pyc or both, let's add a target finalize hooks
that removes all .pyo files.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
[Thomas: add --no-run-if-empty option to xargs, as suggested by Samuel.]
Reviewed-by: Samuel Martin <s.martin49@gmail.com>