packaging: add support for PyOxidizer I've successfully built Mercurial on the development tip of PyOxidizer on Linux and Windows. It mostly "just works" on Linux. Windows is a bit more finicky. In-memory resource files are probably not all working correctly due to bugs in PyOxidizer's naming of modules. PyOxidizer now now supports installing files next to the produced binary. (We do this for templates in the added file.) So a workaround should be available. Also, since the last time I submitted support for PyOxidizer, PyOxidizer gained the ability to auto-generate Rust projects to build executables. So we don't need to worry about vendoring any Rust code to initially support PyOxidizer. However, at some point we will likely want to write our own command line driver that embeds a Python interpreter via PyOxidizer so we can run Rust code outside the confines of a Python interpreter. But that will be a follow-up. I would also like to add packaging.py CLI commands to build PyOxidizer distributions. This can come later, if ever. PyOxidizer's new "targets" feature makes it really easy to define packaging tasks in its Starlark configuration file. While not much is implemented yet, eventually we should be able to produce MSIs, etc using a `pyoxidizer build` one-liner. We'll get there... Differential Revision: https://phab.mercurial-scm.org/D7450