Add lz4 to build dependencies
    
    This commit fixes build failure due to failed "make check".
    
    Our test-compress uses lz4cat. Binary is included in lz4 package that
    used to contain both library and binaries. Since lz4-libs split-off we
    need to explicitly pull-in lz4.
    
    See: http://pkgs.fedoraproject.org/cgit/rpms/lz4.git/commit/?id=34760ea9354a972f946af0282e2c145c660a823c