let cufflinks =   let url =     "http://cole-trapnell-lab.github.io/cufflinks/assets/downloads/cufflinks-2.2.1.Linux_x86_64.tar.gz" in   let witness = witness_file "cufflinks" in   let install_program ~path = KEDSL.Program.(shf "cp * %s" path) in   Installable_tool.make Machine.Tool.Default.cufflinks ~install_program ~url     ~init_program:add_to_dollar_path ~witness