Merge "Write signature size even when it's empty" am: 555c3a7dc7 am: 77f7f00e3d am: 5c8ad6415b am: b7015798b9

Original change: https://android-review.googlesource.com/c/platform/build/+/1938523

Change-Id: I824c50ffea8cd8e122d473b068520d5faf3df014
diff --git a/tools/releasetools/fsverity_metadata_generator.py b/tools/releasetools/fsverity_metadata_generator.py
index a300d2e..fa7cd39 100644
--- a/tools/releasetools/fsverity_metadata_generator.py
+++ b/tools/releasetools/fsverity_metadata_generator.py
@@ -178,6 +178,7 @@
           out.write(sig)
       else:
         out.write(pack('<I', SIG_TYPE_NONE))
+        out.write(pack('<I', 0))
 
       # 4. merkle tree
       with open(merkletree_file, 'rb') as f: