Use a more compact output for overrides and pinned libraries

The entries pinned_libs_* and overrides are gathered using find -ls. However this has the downside to include a lot of information that we usually don't care about like the edit date, the permissions etc...

In an attempt to reduce the steam-runtime-system-info report size, without reducing the about of potentially useful info, this commit replaces the find -ls output with just a recursive list of directories, files and symlinks.