List paths which should be excluded from tarballs

List paths which should be excluded from tarballs

Convert the logic (currently present in the form of "rm -rf" calls in
util/kit.sh) for removing files and directories which are tracked by Git
but redundant in release tarballs into a set of .gitattributes rules
which allow the same effect to be achieved using "git archive".

(cherry picked from commit 925ecb0aae7caa257c8c704364f715e463c44f47)