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- [x] Add new / update outdated documentation

import os
import pprint


def load_sysconfig(sysconfig_name: str):
    _temp = __import__(sysconfig_name, globals(), locals(), ["build_time_vars"], 0)
    config_vars = _temp.build_time_vars
    return config_vars, _temp.__file__


def write_sysconfig(destfile: str, config_vars: dict[str, str]):
    with open(destfile, "w", encoding="utf8") as f:
        f.write(
            "# system configuration generated and used by" " the sysconfig module\n"
        )
        f.write("build_time_vars = ")
        pprint.pprint(config_vars, stream=f)


def adjust_sysconfig(config_vars: dict[str, str]):
    config_vars.update(
        CC="cc",
        MAINCC="cc",
        LDSHARED="cc",
        LINKCC="cc",
        BLDSHARED="cc",
        CXX="c++",
        LDCXXSHARED="c++",
    )


if __name__ == "__main__":
    sysconfig_name = os.environ["SYSCONFIG_NAME"]
    config_vars, file = load_sysconfig(sysconfig_name)
    adjust_sysconfig(config_vars)
    write_sysconfig(file, config_vars)

import os
import pprint


def load_sysconfig(sysconfig_name: str):
    _temp = __import__(sysconfig_name, globals(), locals(), ["build_time_vars"], 0)
    config_vars = _temp.build_time_vars
    return config_vars, _temp.__file__


def write_sysconfig(destfile: str, config_vars: dict[str, str]):
    with open(destfile, "w", encoding="utf8") as f:
        f.write(
            "# system configuration generated and used by" " the sysconfig module\n"
        )
        f.write("build_time_vars = ")
        pprint.pprint(config_vars, stream=f)


def adjust_sysconfig(config_vars: dict[str, str]):
    config_vars.update(
        CC="cc",
        MAINCC="cc",
        LDSHARED="cc",
        LINKCC="cc",
        BLDSHARED="cc",
        CXX="c++",
        LDCXXSHARED="c++",
    )


if __name__ == "__main__":
    sysconfig_name = os.environ["SYSCONFIG_NAME"]
    config_vars, file = load_sysconfig(sysconfig_name)
    adjust_sysconfig(config_vars)
    write_sysconfig(file, config_vars)
