{ "for host":
  { "vars": ["ARCH", "HOST_ARCH", "TARGET_ARCH"]
  , "expression":
    { "type": "let*"
    , "bindings":
      [ [ "BUILD_ARCH"
        , { "type": "var"
          , "name": "TARGET_ARCH"
          , "default": {"type": "var", "name": "ARCH"}
          }
        ]
      , [ "TARGET_ARCH"
        , { "type": "var"
          , "name": "HOST_ARCH"
          , "default": {"type": "var", "name": "ARCH"}
          }
        ]
      ]
    , "body": {"type": "env", "vars": ["BUILD_ARCH", "TARGET_ARCH"]}
    }
  }
, "with fPIC":
  { "doc":
    [ "Transition that enables BUILD_POSITION_INDEPENDENT if config_field"
    , "\"shared\" is not empty."
    ]
  , "var": ["BUILD_OBJECT_ONLY"]
  , "expression":
    { "type": "if"
    , "cond":
      { "type": "and"
      , "$1":
        [ {"type": "FIELD", "name": "shared"}
        , {"type": "not", "$1": {"type": "var", "name": "BUILD_OBJECT_ONLY"}}
        ]
      }
    , "then":
      { "type": "singleton_map"
      , "key": "BUILD_POSITION_INDEPENDENT"
      , "value": true
      }
    , "else": {"type": "empty_map"}
    }
  }
, "with fPIC, not object-only":
  { "doc": ["Like \"with fPIC\", but also clearing BUILD_OBJECT_ONLY"]
  , "var": ["BUILD_OBJECT_ONLY"]
  , "imports": {"with fPIC": "with fPIC"}
  , "expression":
    { "type": "map_union"
    , "$1":
      [ {"type": "CALL_EXPRESSION", "name": "with fPIC"}
      , {"type": "singleton_map", "key": "BUILD_OBJECT_ONLY", "value": null}
      , { "type": "singleton_map"
        , "key": "BUILD_OBJECT_ONLY_DROP_OBJECT_LINKING"
        , "value": null
        }
      ]
    }
  }
, "with fPIC, object-only":
  { "doc":
    ["Like \"with fPIC\", but also unconditionally setting BUILD_OBJECT_ONLY"]
  , "var": ["BUILD_OBJECT_ONLY"]
  , "imports": {"with fPIC": "with fPIC"}
  , "expression":
    { "type": "map_union"
    , "$1":
      [ {"type": "CALL_EXPRESSION", "name": "with fPIC"}
      , {"type": "singleton_map", "key": "BUILD_OBJECT_ONLY", "value": true}
      , { "type": "singleton_map"
        , "key": "BUILD_OBJECT_ONLY_DROP_OBJECT_LINKING"
        , "value": true
        }
      ]
    }
  }
, "target properties":
  { "vars": ["ARCH", "TARGET_ARCH", "ARCH_DISPATCH"]
  , "expression":
    { "type": "let*"
    , "bindings":
      [ [ "TARGET_ARCH"
        , { "type": "var"
          , "name": "TARGET_ARCH"
          , "default": {"type": "var", "name": "ARCH"}
          }
        ]
      ]
    , "body":
      { "type": "if"
      , "cond":
        { "type": "=="
        , "$1": {"type": "var", "name": "TARGET_ARCH"}
        , "$2": null
        }
      , "then": {"type": "empty_map"}
      , "else":
        { "type": "lookup"
        , "map":
          { "type": "var"
          , "name": "ARCH_DISPATCH"
          , "default": {"type": "empty_map"}
          }
        , "key": {"type": "var", "name": "TARGET_ARCH"}
        , "default": {"type": "empty_map"}
        }
      }
    }
  }
, "maybe for host":
  { "vars": ["ARCH", "HOST_ARCH", "TARGET_ARCH", "ARCH_DISPATCH"]
  , "imports":
    {"target properties": "target properties", "for host": "for host"}
  , "expression":
    { "type": "if"
    , "cond": {"type": "CALL_EXPRESSION", "name": "target properties"}
    , "then": {"type": "empty_map"}
    , "else": {"type": "CALL_EXPRESSION", "name": "for host"}
    }
  }
}