build: switch over to file_contexts.bin only

Change all uses of the file_contexts file to use the
file_contexts.bin file instead.

Depends on
   I75a781100082c23536f70ce3603f7de42408b5ba
   I43806d564b83d57f05f5c36c8eba7b1ff4831b04
   Id560d093440a2aba99cef28c20133b35feebf950
   I15660f4b3e4c5cb8ae0ec1498c74d6fcbb9a0400

Change-Id: Iaf8c4b2e420f610425a07f48db7af32bda3f5b3a
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>