Add lz4 to otatools

A call to lz4 was added in http://go/aog/1329115. But the binary
isn't added to otatools, leading to a signing failure.

Bug: 159656873
Test: build otatools
Change-Id: I9cab00f36ce3c39cc174b4c9feffdf360f0364ef
diff --git a/core/Makefile b/core/Makefile
index b46dca1..e5264e1 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -3628,6 +3628,7 @@
   libconscrypt_openjdk_jni \
   lpmake \
   lpunpack \
+  lz4 \
   make_f2fs \
   merge_target_files \
   minigzip \