Fix 'make clean' os Mac OS

Fix 'make clean' os Mac OS

The find command on Mac OS needs a path as first argument, or else
it outputs:

find -name __pycache__ -o -name .pytest_cache | xargs rm -rf
find: illegal option -- n
usage: find [-H | -L | -P] [-EXdsx] [-f path] path ... [expression]
       find [-H | -L | -P] [-EXdsx] -f path [path ...] [expression]
find -name "*.pyc" -o -name "*_clippy.c" | xargs rm -f
find: illegal option -- n
usage: find [-H | -L | -P] [-EXdsx] [-f path] path ... [expression]
       find [-H | -L | -P] [-EXdsx] -f path [path ...] [expression]

Signed-off-by: Ruben Kerkhof <ruben@rubenkerkhof.com>