Unset tag_build and tag_date prior to cutting a release. Fixes #2500.

Author: jaraco

tox.ini

@@ -68,6 +68,8 @@ setenv =
 commands =
 	python -m bootstrap
 	python -c "import path; path.Path('dist').rmtree_p()"
+	# unset tag_build and tag_date pypa/setuptools#2500
+	python setup.py egg_info -Db "" saveopts
 	python -m pep517.build .
 	python -m twine upload dist/*
 	python -m jaraco.develop.create-github-release