Fix content being missed in the build logs

Summary: This fixes an issue where content would be discarded when the content to append is larger than the chunk size limit.

Test Plan: Tested running a remote command that does `I=0; while true; do echo "$I"; I=$[$I+1]; done` and all of the outputted numbers matched the line numbers in the logs.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7537

src/applications/harbormaster/storage/build/HarbormasterBuildLog.php

@@ -95,6 +95,7 @@ final class HarbormasterBuildLog extends HarbormasterDAO
         $current = substr($current, self::CHUNK_BYTE_LIMIT);
         $this->append($part);
       }
+      $this->append($current);
       return;
     }