NoteDbMigrator: Refuse to rebuild if NoteDb writes are disabled

Change-Id: I867d3488a30687b4394b4dea9977b51e34d80e01
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/NoteDbMigrator.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/NoteDbMigrator.java
index 15c72a3..8d43e0b 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/NoteDbMigrator.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/NoteDbMigrator.java
@@ -384,6 +384,9 @@
   }
 
   public void rebuild() throws MigrationException, OrmException {
+    checkState(
+        globalNotesMigration.commitChangeWrites(),
+        "cannot rebuild without noteDb.changes.write=true");
     boolean ok;
     Stopwatch sw = Stopwatch.createStarted();
     log.info("Rebuilding changes in NoteDb");