Assume I run catkin build twice with no modifications, I would expect the second catkin build to complete almost instantaneously, since there's nothing that needs to be done.

I'm not exactly sure whether it's the compiling or the linking that takes a long time. It's definitely faster than doing a clean rebuild, but still slower than I would expect (some packages take 5+ secs).

Is there settings on catkin to make it avoid unnecessarily rebuilding unchanged packages? I've tried running catkin config --env-cache (from here) but didn't see any noticeable change.