Closes https://github.com/pyodide/pyodide/issues/604

This creates an installable `pyodide-build` Python package that we can also upload to PyPi under https://pypi.org/project/pyodide-build/ (currently uploaded the dev version to reserve the name).

There is also the identically named `pyodide-build` CLI command which replaces `bin/pyodide`.

The short term goals is to use fewer hacks with `PATH` and `PYTHONPATH`. Long term goal make it a user facing interface for building packages instead of the Makefile.
Create an installable pyodide-build package. Closes https://github.com/pyodide/pyodide/issues/604

This creates an installable `pyodide-build` Python package that we can also upload to PyPi under https://pypi.org/project/pyodide-build/ (currently uploaded the dev version to reserve the name).

There is also the identically named `pyodide-build` CLI command which replaces `bin/pyodide`.

The short term goals is to use fewer hacks with `PATH` and `PYTHONPATH`. Long term goal make it a user facing interface for building packages instead of the Makefile.
(pyodide-build-cli)=
# pyodide_build CLI

```{eval-rst}
.. sphinx_argparse_cli::
   :module: pyodide_build.__main__
   :func: make_parser
   :prog: bin/pyodide
   :title:
```

(pyodide-build-cli)=
# pyodide-build CLI

```{eval-rst}
.. sphinx_argparse_cli::
   :module: pyodide_build.__main__
   :func: make_parser
   :prog: pyodide-build
   :title:
```
