Fix csv list generation and avoid unnecessary rebuilds

[carlopi]

Fix script that automatically populates http://community-extensions.duckdb.org/extensions/community_extensions.csv (cached version is off due to incompatibilities between linux and macos behaviour of the script).

Also avoid rebuild extension pipeline if no relevant changes are detected.

Next up: changes to docs.hello_world or docs.extended_description should not trigger rebuild.

[carlopi]

Tested on my fork that CSV after this changes looks like: community_extensions.csv