cmake/modules/BuildRocksDB.cmake: enable compressions for rocksdb

cmake/modules/BuildRocksDB.cmake: enable compressions for rocksdb

we should enable them if they are found.

currently, we don't have bzip2 compressor plugin, so it's not detected
in the cmake script. we can always enable it for rocksdb in future.

Fixes: http://tracker.ceph.com/issues/24025
Signed-off-by: Kefu Chai <kchai@redhat.com>
(cherry picked from commit d0b7b52a42bcc70d853f5b5ede66d8d123637e3f)

Conflicts:
	cmake/modules/BuildRocksDB.cmake:
	CMakeLists.txt: in luminous, BuildRocksDB.cmake is not extracted
yet, so update CMakeLists.txt instead.