use find_library instead of hardcoded path for COreServices on MacOS
use find_library instead of hardcoded path for COreServices on MacOS

This is required for successful use with bundling tools like pyinstaller.

pombredanne/billiard,andresriancho/billiard,flaviogrossi/billiard,djsmith42/billiard,jakirkham/billiard,jakirkham/billiard,pombredanne/billiard,djsmith42/billiard,andresriancho/billiard,flaviogrossi/billiard