Reported by Jan Synáček <jan.synacek@gmail.com>
at <https://lists.gnu.org/archive/html/guix-devel/2015-11/msg00522.html>.
* gnu/packages/patches/libarchive-bsdtar-test.patch: New file.
* gnu/packages/backup.scm (libarchive)[source]: Use it.
* gnu-system.am (dist_patch_DATA): Add it.
Ludovic Courtès