BLD Add DISTDIR variable. ### Description

Adds `DISTDIR` env variable that points to the directory where libraries should be copied to when building shared libraries with recipe.

### Checklists

- [x] Add new / update outdated documentation

package:
  name: bleach
  version: 5.0.1
  top-level:
    - bleach
requirements:
  run:
    - webencodings
    - packaging
    - six
source:
  sha256: 085f7f33c15bd408dd9b17a4ad77c577db66d76203e5984b1bd59baeee948b2a
  url: https://files.pythonhosted.org/packages/d4/87/508104336a2bc0c4cfdbdceedc0f44dc72da3abc0460c57e323ddd1b3257/bleach-5.0.1-py3-none-any.whl
about:
  home: https://github.com/mozilla/bleach
  PyPI: https://pypi.org/project/bleach
  summary: An easy safelist-based HTML-sanitizing tool.
  license: Apache Software License

package:
  name: bleach
  version: 5.0.1
  top-level:
    - bleach
requirements:
  run:
    - webencodings
    - packaging
    - six
source:
  sha256: 085f7f33c15bd408dd9b17a4ad77c577db66d76203e5984b1bd59baeee948b2a
  url: https://files.pythonhosted.org/packages/d4/87/508104336a2bc0c4cfdbdceedc0f44dc72da3abc0460c57e323ddd1b3257/bleach-5.0.1-py3-none-any.whl
about:
  home: https://github.com/mozilla/bleach
  PyPI: https://pypi.org/project/bleach
  summary: An easy safelist-based HTML-sanitizing tool.
  license: Apache Software License
