Add handling of Arch and Arch-based distributions (#600)

* Add handling of arch and arch based distributions

* Update src/alire/os_linux/alire-platform.adb

Co-authored-by: Alejandro R Mosteo <amosteo@unizar.es>

* Improve former Arch based Linux distributions detection (#600)

* Check first id then id_like key (#600)

* Update alire-platform.adb

Add a debug trace when falling back to id_like key

* Fix line too long style error (#600)

* Handle the case when id_like is a space separated items list (#600)

* More robust regular expression (#600)

* Simplify processing of id and id_key values (#600)

* Easy_Graph is not available in Official Arch repositories (#600)

Co-authored-by: Alejandro R Mosteo <amosteo@unizar.es>