(archive) with tar doesn't create proper tar ball

[Takashi Kato]

This should create proper tar ball.

(import (rnrs)
        (archive))

(when (file-exists? "foo.tar") (delete-file "foo.tar"))
(call-with-output-archive-file 'tar "foo.tar"
  (lambda (out)
    (append-entry! out (create-entry out "foo"))
    (append-entry! out (create-entry out "foo/bar"))
    (append-entry! out (create-entry out "foo/buz.txt"))))

However, tar(1) can't read generated file properly.

[Takashi Kato]

Don't write data if no data (Fixes #139)

→ <<cset cdb0ad9c0e4e>>