libarchive: fix xmalloc_open_zipped_read_close()

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/archival/libarchive/open_transformer.c b/archival/libarchive/open_transformer.c
index a3018d9..ac7e5db 100644
--- a/archival/libarchive/open_transformer.c
+++ b/archival/libarchive/open_transformer.c
@@ -331,6 +331,9 @@
 		}
 	} else {
 		/* File is not compressed */
+//FIXME: avoid seek
+		xlseek(xstate->src_fd, - xstate->signature_skipped, SEEK_CUR);
+		xstate->signature_skipped = 0;
 		image = xmalloc_read(xstate->src_fd, maxsz_p);
 	}