leveldb: reenable RTTI in build
leveldb: reenable RTTI in build

LevelDB 1.23 forces -fno-rtti in their CMakeLists.txt, which breaks
downstream projects (e.g. Ceph).

See
https://github.com/NixOS/nixpkgs/issues/147801#issuecomment-984627336
for some discussion about this.

OpenSUSE, Fedora, and Arch have all re-enabled RTTI in their packaging
of LevelDB as a result.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs