Print message about the initial query

Helps to see that the delay is actually expected.

scripts/bake/bake_differential.php

@@ -277,6 +277,7 @@ function BakeDifferentialToFile($revision, $diff_id = NULL) {
 
 EnsureOutputDirectoryOrDie();
 
+print('Querying differential revisions from the database ... ' . "\n");
 $revisions = id(new DifferentialRevisionQuery())
   ->setViewer($viewer)
   ->needDiffIDs(true)