Ensure partitions are at least 1 block in size am: 316e7c01c1

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2759626

Change-Id: I859393051397d810c762adc47d7c998263acf5b1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
diff --git a/payload_generator/generate_delta_main.cc b/payload_generator/generate_delta_main.cc
index 5f0c9d2..9afa805 100644
--- a/payload_generator/generate_delta_main.cc
+++ b/payload_generator/generate_delta_main.cc
@@ -470,7 +470,7 @@
     if (part.path.empty()) {
       continue;
     }
-    const auto size = utils::FileSize(part.path);
+    const auto size = std::max<size_t>(utils::FileSize(part.path), kBlockSize);
     if (size % kBlockSize != 0) {
       const auto err =
           truncate(part.path.c_str(), size / kBlockSize * kBlockSize);