nix-store --serve: Implement log size limit

src/libstore/build.cc

@@ -2854,7 +2854,8 @@ void DerivationGoal::handleChildOutput(int fd, const string & data)
             printMsg(lvlError,
                 format("%1% killed after writing more than %2% bytes of log output")
                 % getName() % settings.maxLogSize);
-            timedOut(); // not really a timeout, but close enough
+            killChild();
+            done(BuildResult::LogLimitExceeded);
             return;
         }
         if (verbosity >= settings.buildVerbosity)

src/libstore/store-api.hh

@@ -112,7 +112,8 @@ struct BuildResult
         CachedFailure,
         TimedOut,
         MiscFailure,
-        DependencyFailed
+        DependencyFailed,
+        LogLimitExceeded,
     } status = MiscFailure;
     std::string errorMsg;
     //time_t startTime = 0, stopTime = 0;