{ "toolchain":
  { "type": "export"
  , "target": "toolchain (unexported)"
  , "flexible_config":
    ["ARCH", "TARGET_ARCH", "TOOLCHAIN_CONFIG", "ENV", "BUILD_ARCH"]
  }
, "toolchain (unexported)":
  { "type": "install"
  , "dirs":
    [ [["@", "tools", "", "toolchain"], "."]
    , [["@", "compiler", "", "toolchain"], "compiler"]
    ]
  }
}