[issue29708] support reproducible Python builds

[Éric Araujo]

Change by Éric Araujo <merwok at netwok.org>:


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dependencies: +Reproducible pyc: frozenset is not serialized in a deterministic order, setup.py sdist --format=gztar should use (equivalent of) `gzip -n`, setup.py sdist should honor SOURCE_DATE_EPOCH

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue29708>
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