Remove unused build files on DO

[oktomus]

References:

• https://linux.die.net/man/1/rsync
• https://stackoverflow.com/questions/15687755/how-to-use-rsync-to-copy-only-specific-subdirectories-same-names-in-several-dir
• https://stackoverflow.com/questions/9952000/using-rsync-include-and-exclude-options-to-include-directory-and-file-by-pattern