let sambamba =   Installable_tool.make     Machine.Tool.Default.sambamba     ~archive_is_directory:false     ~url:"https://github.com/lomereiter/sambamba/releases/download/v0.6.5/sambamba_v0.6.5_linux.tar.bz2"     ~init_program:add_to_dollar_path     ~witness:(witness_file "sambamba_v0.6.5")