persistent-cache-cpp: Propagate leveldb

libpersistent-cache-cpp is a static library that still needs to be linked with leveldb.
Propagating this dependency is easier than trying & failing to link.

pkgs/by-name/pe/persistent-cache-cpp/package.nix

@@ -69,6 +69,9 @@ stdenv.mkDerivation (finalAttrs: {
   buildInputs = [
     boost
     lomiri.cmake-extras
+  ];
+
+  propagatedBuildInputs = [
     leveldb
   ];