cpio: fix a bug where we do not extract zero-sized hardlinks

(spotted at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=466771).
Add testsuite entry for that, and another one for another bug:
we do not list hardlinks in cpio -t (not fixed).

function                                             old     new   delta
get_header_cpio                                      884     909     +25
static.saved_hardlinks_created                         -       4      +4
static.pending_hardlinks                               4       -      -4
static.inode                                           4       -      -4
cpio_main                                           1122    1060     -62

1 files changed, 1 insertions, 3 deletions

diff --git a/archival/cpio.c b/archival/cpio.c
index dd9ed756c..2919ff8de 100644
--- a/archival/cpio.c
+++ b/archival/cpio.c
@@ -171,9 +171,7 @@ static int cpio_o(void)
                                 int fd = xopen(name, O_RDONLY);
                                 fflush(stdout);
                                 /* We must abort if file got shorter too! */
-                                if (bb_copyfd_size(fd, STDOUT_FILENO, st.st_size) != st.st_size) {
-                                        bb_error_msg_and_die("I/O error or file '%s' was truncated", name);
-                                }
+                                bb_copyfd_exact_size(fd, STDOUT_FILENO, st.st_size);
                                 bytes += st.st_size;
                                 close(fd);
                         }