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
(cherry picked from commit 3031c299)