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- [x] Add new / update outdated documentation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: pyb2d
  version: 0.7.2
  top-level:
    - b2d

source:
  url: https://github.com/pyb2d/pyb2d/archive/refs/tags/0.7.4.tar.gz
  sha256: 1ddd4bb8c65c94d1c6e6d317ee90ae2b3bd08af7a15771aa1f37dfc82688b104

requirements:
  run:
    - numpy
    - pydantic
    - setuptools

test:
  imports:
    - b2d
    - b2d.testbed

package:
  name: pyb2d
  version: 0.7.2
  top-level:
    - b2d

source:
  url: https://github.com/pyb2d/pyb2d/archive/refs/tags/0.7.4.tar.gz
  sha256: 1ddd4bb8c65c94d1c6e6d317ee90ae2b3bd08af7a15771aa1f37dfc82688b104

requirements:
  run:
    - numpy
    - pydantic
    - setuptools

test:
  imports:
    - b2d
    - b2d.testbed
