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.
package:
  name: beautifulsoup4
  version: 4.9.3
requirements:
  run:
  - soupsieve
source:
  sha256: 84729e322ad1d5b4d25f805bfa05b902dd96450f43842c4e99067d5e1369eb25
  url: https://files.pythonhosted.org/packages/6b/c3/d31704ae558dcca862e4ee8e8388f357af6c9d9acb0cad4ba0fbbd350d9a/beautifulsoup4-4.9.3.tar.gz
test:
  imports:
  - bs4

package:
  name: beautifulsoup4
  version: 4.9.3
requirements:
  run:
  - soupsieve
source:
  sha256: 84729e322ad1d5b4d25f805bfa05b902dd96450f43842c4e99067d5e1369eb25
  url: https://files.pythonhosted.org/packages/6b/c3/d31704ae558dcca862e4ee8e8388f357af6c9d9acb0cad4ba0fbbd350d9a/beautifulsoup4-4.9.3.tar.gz
test:
  imports:
  - bs4
