free builders in VersionSet::DumpManifest

Summary:
Reported by bootcamper
This causes ldb tool to fail the assertion in ~ColumnFamilyData()

Test Plan:
./ldb --db=/tmp/test_db1 --create_if_missing put a1 b1
./ldb manifest_dump --path=/tmp/test_db1/MANIFEST-000001

Reviewers: sdong, yhchiang, rven, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D29517

db/version_set.cc

@@ -2436,7 +2436,6 @@ Status VersionSet::DumpManifest(Options& options, std::string& dscname,
           v->storage_info()->num_levels() - 1);
       cfd->compaction_picker()->SizeBeingCompacted(size_being_compacted);
       v->PrepareApply(*cfd->GetLatestMutableCFOptions(), size_being_compacted);
-      delete builder;
 
       printf("--------------- Column family \"%s\"  (ID %u) --------------\n",
              cfd->GetName().c_str(), (unsigned int)cfd->GetID());
@@ -2451,6 +2450,11 @@ Status VersionSet::DumpManifest(Options& options, std::string& dscname,
       delete v;
     }
 
+    // Free builders
+    for (auto& builder : builders) {
+      delete builder.second;
+    }
+
     next_file_number_.store(next_file + 1);
     last_sequence_ = last_sequence;
     prev_log_number_ = previous_log_number;