For all source `*.py` files installed via either py.install_sources() or
an `install_dir: py.get_install_dir()`, produce `*.pyc` files at install
time. Controllable via a module option.
It can only be used for projects that don't have any rules at all, i.e.
they are purely using Meson to:
- configure files
- run (script?) tests
- install files that exist by the end of the setup stage
This can be useful e.g. for Meson itself, a pure python project.
Eli Schwartz