Creating symlinks in sources/ does not trigger rebuild

[mikn]

Maybe this is well-known, but I just hit a snag with adding some new defaults to my variant (similar to how you manage your defaults in the core bottlerocket repository) and symlinked it from the defaults folder to the variant defaults.d folder, this did not get picked up by the build system that thought nothing had changed.

Maybe an easy fix? Maybe incredibly difficult? But now you know. :)