tools/liblockdep: Build liblockdep from tools/Makefile

add targets to build liblockdep with
  make -C tools liblockdep
like the way other stuff under tools/ can be built

Signed-off-by: S. Lockwood-Childs <sjl@vctlabs.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>