back to build_polyml_component according to 54c6ec4166a4 (amending 808e6ddb5a50);
Notes on building Poly/ML as Isabelle component
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* component skeleton:
$ isabelle build_polyml_component -s sha1 component
* include full source (without symlink), for example:
$ wget https://github.com/polyml/polyml/archive/master.zip