resource: fix build for systems without HWLOC
resource: fix build for systems without HWLOC

Reported by Lucas.

Fixes #90

Signed-off-by: Glauber Costa <7ba9037b0dd006f9408bd45b94707becd5cd4e87@scylladb.com>

avikivity/seastar,kjniemi/seastar,kjniemi/seastar,syuu1228/seastar,cloudius-systems/seastar,dreamsxin/seastar,cloudius-systems/seastar,dreamsxin/seastar,scylladb/seastar,avikivity/seastar,sjperkins/seastar,dreamsxin/seastar,kjniemi/seastar,scylladb/seastar,syuu1228/seastar,sjperkins/seastar,cloudius-systems/seastar,avikivity/seastar,scylladb/seastar,sjperkins/seastar,syuu1228/seastar