Generated Property Files should by default be reproducible

[jdaugherty]

Issue description

There are several property files that are generated by the build - for example the gsp properties, build.info.versions. and the property files generated by various AST. Currently, these property files are only reproducible if the SOURCE_DATE_EPOCH env variable is set. This ticket is to change it so they're always reproducible by default - at least for a given day.

See #14895 for discussion.