Call cpio with --extract-over-symlinks, if present

This is needed to do a local build against the Fedora:20 project:
Fedora 20 ships a filesystem rpm that symlinks /lib64 to /usr/lib64. Moreover, the libgcc rpm,
for example, ships a "/lib64/libgcc_s-4.8.2-20131017.so.1". Thus, openSUSE's cpio cannot
extract the archive (except --extract-over-symlinks is specified).