WIP: CPack/RPM: Allow opting out of including source in debuginfo
Commit b78fcf0d added inclusion of source information in debuginfo packages which is often, but not always, desired. Add an option to exclude all source files from being packaged.
This both fixes the selective source exclusion as well as adds a new option to not consider inclusion of any source at all. The latter option is more complete and straightforward than adding an exclusion for "/", along with more performant since it doesn't need to do the scanning at all.
The branch contains proposed fixes, to be squashed on eventual merge if needed, but easier to review when separated - especially with several blocks of code moving around.
Marked as WIP only because test updates are yet to come, I wanted to get the initial branch up for review.