bpo-45696 introduced a _bootstrap_python interpreter, which was used to create frozen and deepfrozen module files. bpo-45873 dropped the _bootstrap_python interpreter again. Instead Python used an existing Python installation to bootstrap the build.

After some internal discussion we agreed that the approach is flawed and puts too much of a burden on users. Users have to install a fairly recent Python interpreter in order to build 3.11. This makes it harder to build Python on platforms with no or a too old Python version. It also complicated things for container builds and pyenv.

Let's re-introduce a _bootstrap_python interpreter. Cross compiling will still require a build Python interpreter.