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- [x] Add new / update outdated documentation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: unyt
  version: 2.9.3
  top-level:
    - unyt
source:
  url: https://files.pythonhosted.org/packages/ea/78/c05ae0bf409c612c058cbd4a65c77b239ae41f623f0780e19efc691e681a/unyt-2.9.3-py2.py3-none-any.whl
  sha256: 87eaf38dae96a7385fbfab5e875119b5afdbc707bcfa1948710d2e843534ccc7
requirements:
  run:
    - numpy
    - sympy
about:
  home: https://github.com/yt-project/unyt
  PyPI: https://pypi.org/project/unyt
  summary: A package for handling numpy arrays with units
  license: BSD license

package:
  name: unyt
  version: 2.9.3
  top-level:
    - unyt
source:
  url: https://files.pythonhosted.org/packages/ea/78/c05ae0bf409c612c058cbd4a65c77b239ae41f623f0780e19efc691e681a/unyt-2.9.3-py2.py3-none-any.whl
  sha256: 87eaf38dae96a7385fbfab5e875119b5afdbc707bcfa1948710d2e843534ccc7
requirements:
  run:
    - numpy
    - sympy
about:
  home: https://github.com/yt-project/unyt
  PyPI: https://pypi.org/project/unyt
  summary: A package for handling numpy arrays with units
  license: BSD license
