{ "": {"type": "export", "target": "lib"}
, "lib":
  { "type": ["@", "rules", "CC", "library"]
  , "name": ["foo"]
  , "srcs": ["foo.cpp"]
  , "hdrs": ["foo.hpp"]
  }
, "foo.hpp":
  { "type": "generic"
  , "outs": ["foo.hpp"]
  , "cmds":
    ["echo '// generated file' > foo.hpp", "echo 'int foo(int x);' >> foo.hpp"]
  }
}