I wouldn't be surprised if you killed my solution.
I did not killed it because our soluations are the same regarding src_support__extra_files. Because I constantly fear that I miss some header files in scons_manifest.py, I add another target 'update_manifest' to check if any file is missing. The problem with this target is that it would better run in a freshly checked out tree so derived files do not appear as missing. Cheers, Bo