When compiling for debugging, is there a setting somewhere to only compile source that has changed instead of compiling all source?
There are two options when building, Build and Rebuild.
Build means compile and link only the source files that have changed since the last build, while Rebuild means compile and link all source files regardless of whether they changed or not.
Build is the normal thing to do and is faster. Sometimes the versions of project target components can get out of sync and rebuild is necessary to make the build successful.