let strelka =
  let url =
    "ftp://strelka:%27%27@ftp.illumina.com/v1-branch/v1.0.14/strelka_workflow-1.0.14.tar.gz" in
  let strelka_bin = "usr" // "bin" in
  let witness = witness_file @@ strelka_bin // "configureStrelkaWorkflow.pl" in
  let install_program ~path =
    (* C.f. ftp://ftp.illumina.com/v1-branch/v1.0.14/README *)
    KEDSL.Program.(
      shf "./configure --prefix=%s" (path // "usr")
      && sh "make && make install"
    )
  in
  let init_program ~path =
    KEDSL.Program.(shf "export STRELKA_BIN=%s/%s" path strelka_bin) in
  installable_tool Machine.Tool.Default.strelka ~url
    ~init_program ~install_program ~witness