Trace dependencies in build
Openscad has an option:
-d file.deps If the -d option is given, all files accessed while exporting are written to the given deps file in the syntax of a Makefile.
This can be used by Make to properly trace dependencies and figure out when re-builds are necessary and when not. Additionally it may make sense to use Ninja as it's more designed for the style of build we are currently doing, i.e. generating a makefile from a script. It does require users to install Ninja which may be less common than Make (but it does have small statically linked executables available to download for all platforms).