CMake: Place PDBs inside bin

Change-Id: Iee6f7e85a615d27eb9a8190cad39cf7f2e814d63
Reviewed-on: http://review.couchbase.org/33297
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>