[infer][backend] Write the summary to disk in the checkers framework

Summary: It seems that we need to store the summary to disk in `Summary.write_summary`. The previous code was just saving it to the in-memory cache of summaries.

Reviewed By: sblackshear

Differential Revision: D4611090

fbshipit-source-id: 9973679

infer/src/checkers/summary.ml

@@ -41,7 +41,7 @@ module Make (H : Helper) = struct
     | Some global_summary ->
         let payload = H.update_payload summary global_summary.Specs.payload in
         let timestamp = global_summary.timestamp + 1 in
-        Specs.add_summary pname { global_summary with payload; timestamp; }
+        Specs.store_summary pname { global_summary with payload; timestamp; }
     | None ->
         failwithf "Summary for %a should exist, but does not!@." Procname.pp pname