relocatable: Handle directories having subdirectories of binaries
Make the processing of directories less naive so that it can handle a directory
with children that are directories. We now scan for and process binaries in all
directories below the scanned paths rather than only the top-level directory.
This patch moves the meat of the post-processing into a separate function which
is fed paths, process_dir (). Then when the function finds a subdirectory of
the passed path which is itself a directory it recursively calls itself.
