`libringct` was linking against `libcryptonote_basic` for a single, one-line convenience function: `cryptonote::get_blob_hash`.
Since `cryptonote_basic.h` includes `rctTypes.h`, this one function effectively made an explicit circular dependency between
the two libraries. `cryptonote_format_utils.cpp` was including header `rctSigs.h` from `libringct`, when only `rctOps.h` from
`libringct_basic` needed to be included. `libcryptonote_basic` wasn't explictly linking against `libringct_basic` nor
`libringct` like it should have. And `libblockchain_db` wasn't linking against `libcryptonote_basic` like it should have. We
can also downgrade `libblockchain_db`'s dependency on `libringct` to `libringct_basic`.