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- [x] Add new / update outdated documentation

(code-of-conduct)=

```{include} ../../CODE-OF-CONDUCT.md

```

(code-of-conduct)=

```{include} ../../CODE-OF-CONDUCT.md

```
