Warning is emitted when tiles are requested but cannot be used

Added two warnings:
1) Before building the topology map check if tiles are requested but the
   topo method is not hwloc;
2) After building the topology map check if tiles are requested but not
   detected by the library.

Patch by Olga Malysheva

Differential Revision: https://reviews.llvm.org/D40340

llvm-svn: 319374