Add function to extract timestamp from boot image

Also add toybox to otatools list.

Bug: 169169031
Test: build OTA
Change-Id: Ib14dbf46a8385ccf2a9c5a9c6f4e7fa9399cf0ba
diff --git a/tools/releasetools/Android.bp b/tools/releasetools/Android.bp
index 45e0514..e1543e7 100644
--- a/tools/releasetools/Android.bp
+++ b/tools/releasetools/Android.bp
@@ -125,6 +125,9 @@
     required: [
         "brillo_update_payload",
         "checkvintf",
+        "lz4",
+        "toybox",
+        "unpack_bootimg"
     ],
     target: {
         darwin: {