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- [x] Add new / update outdated documentation

From https: // github.com / serge - sans - paille / numpy - benchmarks

From https: // github.com / serge - sans - paille / numpy - benchmarks
