pkgdep/common: Add /usr/lib64 to ld's cache

ld on some distros, e.g., ubuntu1604, doesn't include this particular
path in its SEARCH_DIR list. Add it manually to make sure linking
towards liburing is possible in such a case.

Signed-off-by: Michal Berger <michalx.berger@intel.com>
Change-Id: I82d7ed870ec9ff257dc72a386f950addb5476d1b
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/7022


Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Paul Luse <paul.e.luse@intel.com>
Reviewed-by: Maciej Wawryk <maciejx.wawryk@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Karol Latecki <karol.latecki@intel.com>