Pack system/update_engine/scripts into otatools.zip.

The scripts will be needed by OTA releasetools, for parsing A/B OTA
payload.

Bug: 65261072
Test: `m otatools-package` and check for system/update_engine/scripts.
Change-Id: I5cb54561a5fb0454a37879ca20afa95b82ffdefe
diff --git a/core/Makefile b/core/Makefile
index 305cf4e..11048f5 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -2134,6 +2134,7 @@
   system/extras/verity/build_verity_metadata.py \
   system/extras/ext4_utils/mke2fs.conf \
   external/avb/test/data/testkey_rsa4096.pem \
+  $(shell find system/update_engine/scripts -name \*.pyc -prune -o -type f -print | sort) \
   $(shell find build/target/product/security -type f -name \*.x509.pem -o -name \*.pk8 -o \
       -name verity_key | sort) \
   $(shell find device vendor -type f -name \*.pk8 -o -name verifiedboot\* -o \